net/url_request/url_request_http_job.cc

// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "net/url_request/url_request_http_job.h"

#include "base/base_switches.h"
#include "base/command_line.h"
#include "base/compiler_specific.h"
#include "base/file_util.h"
#include "base/file_version_info.h"
#include "base/message_loop.h"
#include "base/metrics/field_trial.h"
#include "base/metrics/histogram.h"
#include "base/rand_util.h"
#include "base/string_util.h"
#include "base/time.h"
#include "net/base/cert_status_flags.h"
#include "net/base/cookie_store.h"
#include "net/base/filter.h"
#include "net/base/host_port_pair.h"
#include "net/base/load_flags.h"
#include "net/base/mime_util.h"
#include "net/base/net_errors.h"
#include "net/base/net_util.h"
#include "net/base/network_delegate.h"
#include "net/base/sdch_manager.h"
#include "net/base/ssl_cert_request_info.h"
#include "net/base/ssl_config_service.h"
#include "net/base/transport_security_state.h"
#include "net/http/http_mac_signature.h"
#include "net/http/http_request_headers.h"
#include "net/http/http_response_headers.h"
#include "net/http/http_response_info.h"
#include "net/http/http_transaction.h"
#include "net/http/http_transaction_factory.h"
#include "net/http/http_util.h"
#include "net/url_request/https_prober.h"
#include "net/url_request/url_request.h"
#include "net/url_request/url_request_context.h"
#include "net/url_request/url_request_error_job.h"
#include "net/url_request/url_request_redirect_job.h"
#include "net/url_request/url_request_throttler_header_adapter.h"
#include "net/url_request/url_request_throttler_manager.h"

static const char kAvailDictionaryHeader[] = "Avail-Dictionary";

// When histogramming results related to SDCH and/or an SDCH latency test, the
// number of packets for which we need to record arrival times so as to
// calculate interpacket latencies.  We currently are only looking at the
// first few packets, as we're monitoring the impact of the initial TCP
// congestion window on stalling of transmissions.
static const size_t kSdchPacketHistogramCount = 5;

namespace net {

namespace {

void AddAuthorizationHeader(
    const std::vector<CookieStore::CookieInfo>& cookie_infos,
    HttpRequestInfo* request_info) {
  const GURL& url = request_info->url;
  const std::string& method = request_info->method;
  std::string request_uri = HttpUtil::PathForRequest(url);
  const std::string& host = url.host();
  int port = url.EffectiveIntPort();
  for (size_t i = 0; i < cookie_infos.size(); ++i) {
    HttpMacSignature signature;
    if (!signature.AddStateInfo(cookie_infos[i].name,
                                cookie_infos[i].creation_date,
                                cookie_infos[i].mac_key,
                                cookie_infos[i].mac_algorithm)) {
      continue;
    }
    if (!signature.AddHttpInfo(method, request_uri, host, port))
      continue;
    request_info->extra_headers.SetHeader(
        HttpRequestHeaders::kAuthorization,
        signature.GenerateAuthorizationHeader());
    return;  // Only add the first valid header.
  }
}

class HTTPSProberDelegateImpl : public HTTPSProberDelegate {
 public:
  HTTPSProberDelegateImpl(const std::string& host, int max_age,
                          bool include_subdomains,
                          TransportSecurityState* sts)
      : host_(host),
        max_age_(max_age),
        include_subdomains_(include_subdomains),
        sts_(sts) { }

  virtual void ProbeComplete(bool result) {
    if (result) {
      base::Time current_time(base::Time::Now());
      base::TimeDelta max_age_delta = base::TimeDelta::FromSeconds(max_age_);

      TransportSecurityState::DomainState domain_state;
      domain_state.expiry = current_time + max_age_delta;
      domain_state.mode =
          TransportSecurityState::DomainState::MODE_OPPORTUNISTIC;
      domain_state.include_subdomains = include_subdomains_;

      sts_->EnableHost(host_, domain_state);
    }

    delete this;
  }

 private:
  const std::string host_;
  const int max_age_;
  const bool include_subdomains_;
  scoped_refptr<TransportSecurityState> sts_;
};

}  // namespace

class URLRequestHttpJob::HttpFilterContext : public FilterContext {
 public:
  explicit HttpFilterContext(URLRequestHttpJob* job);
  virtual ~HttpFilterContext();

  // FilterContext implementation.
  virtual bool GetMimeType(std::string* mime_type) const;
  virtual bool GetURL(GURL* gurl) const;
  virtual base::Time GetRequestTime() const;
  virtual bool IsCachedContent() const;
  virtual bool IsDownload() const;
  virtual bool IsSdchResponse() const;
  virtual int64 GetByteReadCount() const;
  virtual int GetResponseCode() const;
  virtual void RecordPacketStats(StatisticSelector statistic) const;

  // Method to allow us to reset filter context for a response that should have
  // been SDCH encoded when there is an update due to an explicit HTTP header.
  void ResetSdchResponseToFalse();

 private:
  URLRequestHttpJob* job_;

  DISALLOW_COPY_AND_ASSIGN(HttpFilterContext);
};

URLRequestHttpJob::HttpFilterContext::HttpFilterContext(URLRequestHttpJob* job)
    : job_(job) {
  DCHECK(job_);
}

URLRequestHttpJob::HttpFilterContext::~HttpFilterContext() {
}

bool URLRequestHttpJob::HttpFilterContext::GetMimeType(
    std::string* mime_type) const {
  return job_->GetMimeType(mime_type);
}

bool URLRequestHttpJob::HttpFilterContext::GetURL(GURL* gurl) const {
  if (!job_->request())
    return false;
  *gurl = job_->request()->url();
  return true;
}

base::Time URLRequestHttpJob::HttpFilterContext::GetRequestTime() const {
  return job_->request() ? job_->request()->request_time() : base::Time();
}

bool URLRequestHttpJob::HttpFilterContext::IsCachedContent() const {
  return job_->is_cached_content_;
}

bool URLRequestHttpJob::HttpFilterContext::IsDownload() const {
  return (job_->request_info_.load_flags & LOAD_IS_DOWNLOAD) != 0;
}

void URLRequestHttpJob::HttpFilterContext::ResetSdchResponseToFalse() {
  DCHECK(job_->sdch_dictionary_advertised_);
  job_->sdch_dictionary_advertised_ = false;
}

bool URLRequestHttpJob::HttpFilterContext::IsSdchResponse() const {
  return job_->sdch_dictionary_advertised_;
}

int64 URLRequestHttpJob::HttpFilterContext::GetByteReadCount() const {
  return job_->filter_input_byte_count();
}

int URLRequestHttpJob::HttpFilterContext::GetResponseCode() const {
  return job_->GetResponseCode();
}

void URLRequestHttpJob::HttpFilterContext::RecordPacketStats(
    StatisticSelector statistic) const {
  job_->RecordPacketStats(statistic);
}

// TODO(darin): make sure the port blocking code is not lost
// static
URLRequestJob* URLRequestHttpJob::Factory(URLRequest* request,
                                          const std::string& scheme) {
  DCHECK(scheme == "http" || scheme == "https");

  int port = request->url().IntPort();
  if (!IsPortAllowedByDefault(port) && !IsPortAllowedByOverride(port))
    return new URLRequestErrorJob(request, ERR_UNSAFE_PORT);

  if (!request->context() ||
      !request->context()->http_transaction_factory()) {
    NOTREACHED() << "requires a valid context";
    return new URLRequestErrorJob(request, ERR_INVALID_ARGUMENT);
  }

  TransportSecurityState::DomainState domain_state;
  if (scheme == "http" &&
      request->context()->transport_security_state() &&
      request->context()->transport_security_state()->IsEnabledForHost(
          &domain_state,
          request->url().host(),
          SSLConfigService::IsSNIAvailable(
              request->context()->ssl_config_service()))) {
    if (domain_state.mode ==
         TransportSecurityState::DomainState::MODE_STRICT) {
      DCHECK_EQ(request->url().scheme(), "http");
      url_canon::Replacements<char> replacements;
      static const char kNewScheme[] = "https";
      replacements.SetScheme(kNewScheme,
                             url_parse::Component(0, strlen(kNewScheme)));
      GURL new_location = request->url().ReplaceComponents(replacements);
      return new URLRequestRedirectJob(request, new_location);
    } else {
      // TODO(agl): implement opportunistic HTTPS upgrade.
    }
  }

  return new URLRequestHttpJob(request);
}


URLRequestHttpJob::URLRequestHttpJob(URLRequest* request)
    : URLRequestJob(request),
      response_info_(NULL),
      response_cookies_save_index_(0),
      proxy_auth_state_(AUTH_STATE_DONT_NEED_AUTH),
      server_auth_state_(AUTH_STATE_DONT_NEED_AUTH),
      ALLOW_THIS_IN_INITIALIZER_LIST(start_callback_(
          this, &URLRequestHttpJob::OnStartCompleted)),
      ALLOW_THIS_IN_INITIALIZER_LIST(read_callback_(
          this, &URLRequestHttpJob::OnReadCompleted)),
      ALLOW_THIS_IN_INITIALIZER_LIST(notify_before_headers_sent_callback_(
          this, &URLRequestHttpJob::NotifyBeforeSendHeadersCallback)),
      read_in_progress_(false),
      transaction_(NULL),
      throttling_entry_(URLRequestThrottlerManager::GetInstance()->
          RegisterRequestUrl(request->url())),
      sdch_dictionary_advertised_(false),
      sdch_test_activated_(false),
      sdch_test_control_(false),
      is_cached_content_(false),
      request_creation_time_(),
      packet_timing_enabled_(false),
      done_(false),
      bytes_observed_in_packets_(0),
      packet_times_(),
      request_time_snapshot_(),
      final_packet_time_(),
      observed_packet_count_(0),
      ALLOW_THIS_IN_INITIALIZER_LIST(
          filter_context_(new HttpFilterContext(this))),
      ALLOW_THIS_IN_INITIALIZER_LIST(method_factory_(this)) {
  ResetTimer();
}

void URLRequestHttpJob::NotifyHeadersComplete() {
  DCHECK(!response_info_);

  response_info_ = transaction_->GetResponseInfo();

  // Save boolean, as we'll need this info at destruction time, and filters may
  // also need this info.
  is_cached_content_ = response_info_->was_cached;

  if (!is_cached_content_) {
    URLRequestThrottlerHeaderAdapter response_adapter(
        response_info_->headers);
    throttling_entry_->UpdateWithResponse(request_info_.url.host(),
                                          &response_adapter);
  }

  ProcessStrictTransportSecurityHeader();

  if (SdchManager::Global() &&
      SdchManager::Global()->IsInSupportedDomain(request_->url())) {
    static const std::string name = "Get-Dictionary";
    std::string url_text;
    void* iter = NULL;
    // TODO(jar): We need to not fetch dictionaries the first time they are
    // seen, but rather wait until we can justify their usefulness.
    // For now, we will only fetch the first dictionary, which will at least
    // require multiple suggestions before we get additional ones for this site.
    // Eventually we should wait until a dictionary is requested several times
    // before we even download it (so that we don't waste memory or bandwidth).
    if (response_info_->headers->EnumerateHeader(&iter, name, &url_text)) {
      // request_->url() won't be valid in the destructor, so we use an
      // alternate copy.
      DCHECK_EQ(request_->url(), request_info_.url);
      // Resolve suggested URL relative to request url.
      sdch_dictionary_url_ = request_info_.url.Resolve(url_text);
    }
  }

  // The HTTP transaction may be restarted several times for the purposes
  // of sending authorization information. Each time it restarts, we get
  // notified of the headers completion so that we can update the cookie store.
  if (transaction_->IsReadyToRestartForAuth()) {
    DCHECK(!response_info_->auth_challenge.get());
    // TODO(battre): This breaks the webrequest API for
    // URLRequestTestHTTP.BasicAuthWithCookies
    // where OnBeforeSendHeaders -> OnRequestSent -> OnBeforeSendHeaders
    // occurs.
    RestartTransactionWithAuth(string16(), string16());
    return;
  }

  URLRequestJob::NotifyHeadersComplete();
}

void URLRequestHttpJob::NotifyDone(const URLRequestStatus& status) {
  DoneWithRequest(FINISHED);
  URLRequestJob::NotifyDone(status);
}

void URLRequestHttpJob::DestroyTransaction() {
  DCHECK(transaction_.get());

  DoneWithRequest(ABORTED);
  transaction_.reset();
  response_info_ = NULL;
  context_ = NULL;
}

void URLRequestHttpJob::StartTransaction() {
  if (request_->context() && request_->context()->network_delegate()) {
    int rv = request_->context()->network_delegate()->NotifyBeforeSendHeaders(
        request_, &notify_before_headers_sent_callback_,
        &request_info_.extra_headers);
    // If an extension blocks the request, we rely on the callback to
    // StartTransactionInternal().
    if (rv == ERR_IO_PENDING) {
      request_->net_log().BeginEvent(
          NetLog::TYPE_URL_REQUEST_BLOCKED_ON_DELEGATE, NULL);
      return;
    }
  }
  StartTransactionInternal();
}

void URLRequestHttpJob::NotifyBeforeSendHeadersCallback(int result) {
  request_->net_log().EndEvent(
      NetLog::TYPE_URL_REQUEST_BLOCKED_ON_DELEGATE, NULL);

  if (result == OK) {
    StartTransactionInternal();
  } else {
    // TODO(battre): Allow passing information of the extension that canceled
    // the event.
    request_->net_log().AddEvent(NetLog::TYPE_CANCELLED,
        make_scoped_refptr(new NetLogStringParameter("source", "delegate")));
    NotifyCanceled();
  }
}

void URLRequestHttpJob::StartTransactionInternal() {
  // NOTE: This method assumes that request_info_ is already setup properly.

  // If we already have a transaction, then we should restart the transaction
  // with auth provided by username_ and password_.

  int rv;

  if (transaction_.get()) {
    rv = transaction_->RestartWithAuth(username_, password_, &start_callback_);
    username_.clear();
    password_.clear();
  } else {
    DCHECK(request_->context());
    DCHECK(request_->context()->http_transaction_factory());

    rv = request_->context()->http_transaction_factory()->CreateTransaction(
        &transaction_);
    if (rv == OK) {
      if (!URLRequestThrottlerManager::GetInstance()->enforce_throttling() ||
          !throttling_entry_->IsDuringExponentialBackoff()) {
        rv = transaction_->Start(
            &request_info_, &start_callback_, request_->net_log());
        start_time_ = base::TimeTicks::Now();
      } else {
        // Special error code for the exponential back-off module.
        rv = ERR_TEMPORARILY_THROTTLED;
      }
      // Make sure the context is alive for the duration of the
      // transaction.
      context_ = request_->context();
    }
  }

  if (rv == ERR_IO_PENDING)
    return;

  // The transaction started synchronously, but we need to notify the
  // URLRequest delegate via the message loop.
  MessageLoop::current()->PostTask(
      FROM_HERE,
      method_factory_.NewRunnableMethod(
          &URLRequestHttpJob::OnStartCompleted, rv));
}

void URLRequestHttpJob::AddExtraHeaders() {
  // Supply Accept-Encoding field only if it is not already provided.
  // It should be provided IF the content is known to have restrictions on
  // potential encoding, such as streaming multi-media.
  // For details see bug 47381.
  // TODO(jar, enal): jpeg files etc. should set up a request header if
  // possible. Right now it is done only by buffered_resource_loader and
  // simple_data_source.
  if (!request_info_.extra_headers.HasHeader(
      HttpRequestHeaders::kAcceptEncoding)) {
    bool advertise_sdch = SdchManager::Global() &&
        SdchManager::Global()->IsInSupportedDomain(request_->url());
    std::string avail_dictionaries;
    if (advertise_sdch) {
      SdchManager::Global()->GetAvailDictionaryList(request_->url(),
                                                    &avail_dictionaries);

      // The AllowLatencyExperiment() is only true if we've successfully done a
      // full SDCH compression recently in this browser session for this host.
      // Note that for this path, there might be no applicable dictionaries,
      // and hence we can't participate in the experiment.
      if (!avail_dictionaries.empty() &&
          SdchManager::Global()->AllowLatencyExperiment(request_->url())) {
        // We are participating in the test (or control), and hence we'll
        // eventually record statistics via either SDCH_EXPERIMENT_DECODE or
        // SDCH_EXPERIMENT_HOLDBACK, and we'll need some packet timing data.
        packet_timing_enabled_ = true;
        if (base::RandDouble() < .01) {
          sdch_test_control_ = true;  // 1% probability.
          advertise_sdch = false;
        } else {
          sdch_test_activated_ = true;
        }
      }
    }

    // Supply Accept-Encoding headers first so that it is more likely that they
    // will be in the first transmitted packet.  This can sometimes make it
    // easier to filter and analyze the streams to assure that a proxy has not
    // damaged these headers.  Some proxies deliberately corrupt Accept-Encoding
    // headers.
    if (!advertise_sdch) {
      // Tell the server what compression formats we support (other than SDCH).
      request_info_.extra_headers.SetHeader(
          HttpRequestHeaders::kAcceptEncoding, "gzip,deflate");
    } else {
      // Include SDCH in acceptable list.
      request_info_.extra_headers.SetHeader(
          HttpRequestHeaders::kAcceptEncoding, "gzip,deflate,sdch");
      if (!avail_dictionaries.empty()) {
        request_info_.extra_headers.SetHeader(
            kAvailDictionaryHeader,
            avail_dictionaries);
        sdch_dictionary_advertised_ = true;
        // Since we're tagging this transaction as advertising a dictionary,
        // we'll definitely employ an SDCH filter (or tentative sdch filter)
        // when we get a response.  When done, we'll record histograms via
        // SDCH_DECODE or SDCH_PASSTHROUGH.  Hence we need to record packet
        // arrival times.
        packet_timing_enabled_ = true;
      }
    }
  }

  const URLRequestContext* context = request_->context();
  if (context) {
    // Only add default Accept-Language and Accept-Charset if the request
    // didn't have them specified.
    if (!context->accept_language().empty()) {
      request_info_.extra_headers.SetHeaderIfMissing(
          HttpRequestHeaders::kAcceptLanguage,
          context->accept_language());
    }
    if (!context->accept_charset().empty()) {
      request_info_.extra_headers.SetHeaderIfMissing(
          HttpRequestHeaders::kAcceptCharset,
          context->accept_charset());
    }
  }
}

void URLRequestHttpJob::AddCookieHeaderAndStart() {
  // No matter what, we want to report our status as IO pending since we will
  // be notifying our consumer asynchronously via OnStartCompleted.
  SetStatus(URLRequestStatus(URLRequestStatus::IO_PENDING, 0));

  // If the request was destroyed, then there is no more work to do.
  if (!request_)
    return;

  bool allow = true;
  if ((request_info_.load_flags & LOAD_DO_NOT_SEND_COOKIES) ||
      !CanGetCookies()) {
    allow = false;
  }

  if (request_->context()->cookie_store() && allow) {
    CookieOptions options;
    options.set_include_httponly();
    std::string cookie_line;
    std::vector<CookieStore::CookieInfo> cookie_infos;
    request_->context()->cookie_store()->GetCookiesWithInfo(
        request_->url(), options, &cookie_line, &cookie_infos);
    if (!cookie_line.empty()) {
      request_info_.extra_headers.SetHeader(
          HttpRequestHeaders::kCookie, cookie_line);
    }
    if (URLRequest::AreMacCookiesEnabled())
      AddAuthorizationHeader(cookie_infos, &request_info_);
  }
  // We may have been canceled within CanGetCookies.
  if (GetStatus().is_success()) {
    StartTransaction();
  } else {
    NotifyCanceled();
  }
}

void URLRequestHttpJob::SaveCookiesAndNotifyHeadersComplete() {
  DCHECK(transaction_.get());

  const HttpResponseInfo* response_info = transaction_->GetResponseInfo();
  DCHECK(response_info);

  response_cookies_.clear();
  response_cookies_save_index_ = 0;

  FetchResponseCookies(response_info, &response_cookies_);

  // Now, loop over the response cookies, and attempt to persist each.
  SaveNextCookie();
}

void URLRequestHttpJob::SaveNextCookie() {
  if (response_cookies_save_index_ == response_cookies_.size()) {
    response_cookies_.clear();
    response_cookies_save_index_ = 0;
    SetStatus(URLRequestStatus());  // Clear the IO_PENDING status
    NotifyHeadersComplete();
    return;
  }

  // No matter what, we want to report our status as IO pending since we will
  // be notifying our consumer asynchronously via OnStartCompleted.
  SetStatus(URLRequestStatus(URLRequestStatus::IO_PENDING, 0));

  CookieOptions options;
  if (!(request_info_.load_flags & LOAD_DO_NOT_SAVE_COOKIES) &&
      request_->context()->cookie_store()) {
    CookieOptions options;
    options.set_include_httponly();
    if (CanSetCookie(
        response_cookies_[response_cookies_save_index_], &options)) {
      request_->context()->cookie_store()->SetCookieWithOptions(
          request_->url(), response_cookies_[response_cookies_save_index_],
          options);
    }
  }

  response_cookies_save_index_++;
  // We may have been canceled within OnSetCookie.
  if (GetStatus().is_success()) {
    SaveNextCookie();
  } else {
    NotifyCanceled();
  }
}

void URLRequestHttpJob::FetchResponseCookies(
    const HttpResponseInfo* response_info,
    std::vector<std::string>* cookies) {
  std::string name = "Set-Cookie";
  std::string value;

  void* iter = NULL;
  while (response_info->headers->EnumerateHeader(&iter, name, &value)) {
    if (!value.empty())
      cookies->push_back(value);
  }
}

void URLRequestHttpJob::ProcessStrictTransportSecurityHeader() {
  DCHECK(response_info_);

  const URLRequestContext* ctx = request_->context();
  if (!ctx || !ctx->transport_security_state())
    return;

  const bool https = response_info_->ssl_info.is_valid();
  const bool valid_https =
      https && !IsCertStatusError(response_info_->ssl_info.cert_status);

  std::string name = "Strict-Transport-Security";
  std::string value;

  int max_age;
  bool include_subdomains;

  void* iter = NULL;
  while (response_info_->headers->EnumerateHeader(&iter, name, &value)) {
    const bool ok = TransportSecurityState::ParseHeader(
        value, &max_age, &include_subdomains);
    if (!ok)
      continue;
    // We will only accept strict mode if we saw the header from an HTTPS
    // connection with no certificate problems.
    if (!valid_https)
      continue;
    base::Time current_time(base::Time::Now());
    base::TimeDelta max_age_delta = base::TimeDelta::FromSeconds(max_age);

    TransportSecurityState::DomainState domain_state;
    domain_state.expiry = current_time + max_age_delta;
    domain_state.mode = TransportSecurityState::DomainState::MODE_STRICT;
    domain_state.include_subdomains = include_subdomains;

    ctx->transport_security_state()->EnableHost(request_info_.url.host(),
                                                domain_state);
  }

  // TODO(agl): change this over when we have fixed things at the server end.
  // The string should be "Opportunistic-Transport-Security";
  name = "X-Bodge-Transport-Security";

  while (response_info_->headers->EnumerateHeader(&iter, name, &value)) {
    const bool ok = TransportSecurityState::ParseHeader(
        value, &max_age, &include_subdomains);
    if (!ok)
      continue;
    // If we saw an opportunistic request over HTTPS, then clearly we can make
    // HTTPS connections to the host so we should remember this.
    if (https) {
      base::Time current_time(base::Time::Now());
      base::TimeDelta max_age_delta = base::TimeDelta::FromSeconds(max_age);

      TransportSecurityState::DomainState domain_state;
      domain_state.expiry = current_time + max_age_delta;
      domain_state.mode =
          TransportSecurityState::DomainState::MODE_SPDY_ONLY;
      domain_state.include_subdomains = include_subdomains;

      ctx->transport_security_state()->EnableHost(request_info_.url.host(),
                                                  domain_state);
      continue;
    }

    if (!request())
      break;

    // At this point, we have a request for opportunistic encryption over HTTP.
    // In this case we need to probe to check that we can make HTTPS
    // connections to that host.
    HTTPSProber* const prober = HTTPSProber::GetInstance();
    if (prober->HaveProbed(request_info_.url.host()) ||
        prober->InFlight(request_info_.url.host())) {
      continue;
    }

    HTTPSProberDelegateImpl* delegate =
        new HTTPSProberDelegateImpl(request_info_.url.host(), max_age,
                                    include_subdomains,
                                    ctx->transport_security_state());
    if (!prober->ProbeHost(request_info_.url.host(), request()->context(),
                           delegate)) {
      delete delegate;
    }
  }
}

void URLRequestHttpJob::OnStartCompleted(int result) {
  RecordTimer();

  // If the request was destroyed, then there is no more work to do.
  if (!request_)
    return;

  // If the transaction was destroyed, then the job was cancelled, and
  // we can just ignore this notification.
  if (!transaction_.get())
    return;

  // Clear the IO_PENDING status
  SetStatus(URLRequestStatus());

  // Take care of any mandates for public key pinning.
  // TODO(agl): we might have an issue here where a request for foo.example.com
  // merges into a SPDY connection to www.example.com, and gets a different
  // certificate.
  const SSLInfo& ssl_info = transaction_->GetResponseInfo()->ssl_info;
  if (result == OK &&
      ssl_info.is_valid() &&
      ssl_info.is_issued_by_known_root &&
      context_->transport_security_state()) {
    TransportSecurityState::DomainState domain_state;
    if (context_->transport_security_state()->HasPinsForHost(
            &domain_state,
            request_->url().host(),
            SSLConfigService::IsSNIAvailable(
                context_->ssl_config_service()))) {
      if (!domain_state.IsChainOfPublicKeysPermitted(
              ssl_info.public_key_hashes)) {
        result = ERR_CERT_INVALID;
        UMA_HISTOGRAM_BOOLEAN("Net.CertificatePinSuccess", false);
      } else {
        UMA_HISTOGRAM_BOOLEAN("Net.CertificatePinSuccess", true);
      }
    }
  }

  if (result == OK) {
    SaveCookiesAndNotifyHeadersComplete();
  } else if (ShouldTreatAsCertificateError(result)) {
    // We encountered an SSL certificate error.  Ask our delegate to decide
    // what we should do.
    // TODO(wtc): also pass ssl_info.cert_status, or just pass the whole
    // ssl_info.
    NotifySSLCertificateError(
        result, transaction_->GetResponseInfo()->ssl_info.cert);
  } else if (result == ERR_SSL_CLIENT_AUTH_CERT_NEEDED) {
    NotifyCertificateRequested(
        transaction_->GetResponseInfo()->cert_request_info);
  } else {
    NotifyStartError(URLRequestStatus(URLRequestStatus::FAILED, result));
  }
}

void URLRequestHttpJob::OnReadCompleted(int result) {
  read_in_progress_ = false;

  if (ShouldFixMismatchedContentLength(result))
    result = 0;

  if (result == 0) {
    NotifyDone(URLRequestStatus());
  } else if (result < 0) {
    NotifyDone(URLRequestStatus(URLRequestStatus::FAILED, result));
  } else {
    // Clear the IO_PENDING status
    SetStatus(URLRequestStatus());
  }

  NotifyReadComplete(result);
}

bool URLRequestHttpJob::ShouldTreatAsCertificateError(int result) {
  if (!IsCertificateError(result))
    return false;

  // Revocation check failures are always certificate errors, even if the host
  // is using Strict-Transport-Security.
  if (result == ERR_CERT_UNABLE_TO_CHECK_REVOCATION)
    return true;

  // Check whether our context is using Strict-Transport-Security.
  if (!context_->transport_security_state())
    return true;

  TransportSecurityState::DomainState domain_state;
  // TODO(agl): don't ignore opportunistic mode.
  const bool r = context_->transport_security_state()->IsEnabledForHost(
      &domain_state, request_info_.url.host(),
      SSLConfigService::IsSNIAvailable(context_->ssl_config_service()));

  return !r || domain_state.mode ==
               TransportSecurityState::DomainState::MODE_OPPORTUNISTIC;
}

void URLRequestHttpJob::RestartTransactionWithAuth(
    const string16& username,
    const string16& password) {
  username_ = username;
  password_ = password;

  // These will be reset in OnStartCompleted.
  response_info_ = NULL;
  response_cookies_.clear();

  ResetTimer();

  // Update the cookies, since the cookie store may have been updated from the
  // headers in the 401/407. Since cookies were already appended to
  // extra_headers, we need to strip them out before adding them again.
  request_info_.extra_headers.RemoveHeader(
      HttpRequestHeaders::kCookie);

  AddCookieHeaderAndStart();
}

void URLRequestHttpJob::SetUpload(UploadData* upload) {
  DCHECK(!transaction_.get()) << "cannot change once started";
  request_info_.upload_data = upload;
}

void URLRequestHttpJob::SetExtraRequestHeaders(
    const HttpRequestHeaders& headers) {
  DCHECK(!transaction_.get()) << "cannot change once started";
  request_info_.extra_headers.CopyFrom(headers);
}

void URLRequestHttpJob::Start() {
  DCHECK(!transaction_.get());

  // Ensure that we do not send username and password fields in the referrer.
  GURL referrer(request_->GetSanitizedReferrer());

  request_info_.url = request_->url();
  request_info_.method = request_->method();
  request_info_.load_flags = request_->load_flags();
  request_info_.priority = request_->priority();
  request_info_.request_id = request_->identifier();

  // Strip Referer from request_info_.extra_headers to prevent, e.g., plugins
  // from overriding headers that are controlled using other means. Otherwise a
  // plugin could set a referrer although sending the referrer is inhibited.
  request_info_.extra_headers.RemoveHeader(HttpRequestHeaders::kReferer);

  // Our consumer should have made sure that this is a safe referrer.  See for
  // instance WebCore::FrameLoader::HideReferrer.
  if (referrer.is_valid()) {
    request_info_.extra_headers.SetHeader(HttpRequestHeaders::kReferer,
                                          referrer.spec());
  }

  if (request_->context()) {
    request_info_.extra_headers.SetHeaderIfMissing(
        HttpRequestHeaders::kUserAgent,
        request_->context()->GetUserAgent(request_->url()));
  }

  AddExtraHeaders();
  AddCookieHeaderAndStart();
}

void URLRequestHttpJob::Kill() {
  if (!transaction_.get())
    return;

  DestroyTransaction();
  URLRequestJob::Kill();
}

LoadState URLRequestHttpJob::GetLoadState() const {
  return transaction_.get() ?
      transaction_->GetLoadState() : LOAD_STATE_IDLE;
}

uint64 URLRequestHttpJob::GetUploadProgress() const {
  return transaction_.get() ? transaction_->GetUploadProgress() : 0;
}

bool URLRequestHttpJob::GetMimeType(std::string* mime_type) const {
  DCHECK(transaction_.get());

  if (!response_info_)
    return false;

  return response_info_->headers->GetMimeType(mime_type);
}

bool URLRequestHttpJob::GetCharset(std::string* charset) {
  DCHECK(transaction_.get());

  if (!response_info_)
    return false;

  return response_info_->headers->GetCharset(charset);
}

void URLRequestHttpJob::GetResponseInfo(HttpResponseInfo* info) {
  DCHECK(request_);
  DCHECK(transaction_.get());

  if (response_info_)
    *info = *response_info_;
}

bool URLRequestHttpJob::GetResponseCookies(
    std::vector<std::string>* cookies) {
  DCHECK(transaction_.get());

  if (!response_info_)
    return false;

  // TODO(darin): Why are we extracting response cookies again?  Perhaps we
  // should just leverage response_cookies_.

  cookies->clear();
  FetchResponseCookies(response_info_, cookies);
  return true;
}

int URLRequestHttpJob::GetResponseCode() const {
  DCHECK(transaction_.get());

  if (!response_info_)
    return -1;

  return response_info_->headers->response_code();
}

Filter* URLRequestHttpJob::SetupFilter() const {
  DCHECK(transaction_.get());
  if (!response_info_)
    return NULL;

  std::vector<Filter::FilterType> encoding_types;
  std::string encoding_type;
  void* iter = NULL;
  while (response_info_->headers->EnumerateHeader(&iter, "Content-Encoding",
                                                  &encoding_type)) {
    encoding_types.push_back(Filter::ConvertEncodingToType(encoding_type));
  }

  if (filter_context_->IsSdchResponse()) {
    // We are wary of proxies that discard or damage SDCH encoding.  If a server
    // explicitly states that this is not SDCH content, then we can correct our
    // assumption that this is an SDCH response, and avoid the need to recover
    // as though the content is corrupted (when we discover it is not SDCH
    // encoded).
    std::string sdch_response_status;
    iter = NULL;
    while (response_info_->headers->EnumerateHeader(&iter, "X-Sdch-Encode",
                                                    &sdch_response_status)) {
      if (sdch_response_status == "0") {
        filter_context_->ResetSdchResponseToFalse();
        break;
      }
    }
  }

  // Even if encoding types are empty, there is a chance that we need to add
  // some decoding, as some proxies strip encoding completely. In such cases,
  // we may need to add (for example) SDCH filtering (when the context suggests
  // it is appropriate).
  Filter::FixupEncodingTypes(*filter_context_, &encoding_types);

  return !encoding_types.empty()
      ? Filter::Factory(encoding_types, *filter_context_) : NULL;
}

bool URLRequestHttpJob::IsSafeRedirect(const GURL& location) {
  // We only allow redirects to certain "safe" protocols.  This does not
  // restrict redirects to externally handled protocols.  Our consumer would
  // need to take care of those.

  if (!URLRequest::IsHandledURL(location))
    return true;

  static const char* kSafeSchemes[] = {
    "http",
    "https",
    "ftp"
  };

  for (size_t i = 0; i < arraysize(kSafeSchemes); ++i) {
    if (location.SchemeIs(kSafeSchemes[i]))
      return true;
  }

  return false;
}

bool URLRequestHttpJob::NeedsAuth() {
  int code = GetResponseCode();
  if (code == -1)
    return false;

  // Check if we need either Proxy or WWW Authentication.  This could happen
  // because we either provided no auth info, or provided incorrect info.
  switch (code) {
    case 407:
      if (proxy_auth_state_ == AUTH_STATE_CANCELED)
        return false;
      proxy_auth_state_ = AUTH_STATE_NEED_AUTH;
      return true;
    case 401:
      if (server_auth_state_ == AUTH_STATE_CANCELED)
        return false;
      server_auth_state_ = AUTH_STATE_NEED_AUTH;
      return true;
  }
  return false;
}

void URLRequestHttpJob::GetAuthChallengeInfo(
    scoped_refptr<AuthChallengeInfo>* result) {
  DCHECK(transaction_.get());
  DCHECK(response_info_);

  // sanity checks:
  DCHECK(proxy_auth_state_ == AUTH_STATE_NEED_AUTH ||
         server_auth_state_ == AUTH_STATE_NEED_AUTH);
  DCHECK(response_info_->headers->response_code() == 401 ||
         response_info_->headers->response_code() == 407);

  *result = response_info_->auth_challenge;
}

void URLRequestHttpJob::SetAuth(const string16& username,
                                const string16& password) {
  DCHECK(transaction_.get());

  // Proxy gets set first, then WWW.
  if (proxy_auth_state_ == AUTH_STATE_NEED_AUTH) {
    proxy_auth_state_ = AUTH_STATE_HAVE_AUTH;
  } else {
    DCHECK_EQ(server_auth_state_, AUTH_STATE_NEED_AUTH);
    server_auth_state_ = AUTH_STATE_HAVE_AUTH;
  }

  RestartTransactionWithAuth(username, password);
}

void URLRequestHttpJob::CancelAuth() {
  // Proxy gets set first, then WWW.
  if (proxy_auth_state_ == AUTH_STATE_NEED_AUTH) {
    proxy_auth_state_ = AUTH_STATE_CANCELED;
  } else {
    DCHECK_EQ(server_auth_state_, AUTH_STATE_NEED_AUTH);
    server_auth_state_ = AUTH_STATE_CANCELED;
  }

  // These will be reset in OnStartCompleted.
  response_info_ = NULL;
  response_cookies_.clear();

  ResetTimer();

  // OK, let the consumer read the error page...
  //
  // Because we set the AUTH_STATE_CANCELED flag, NeedsAuth will return false,
  // which will cause the consumer to receive OnResponseStarted instead of
  // OnAuthRequired.
  //
  // We have to do this via InvokeLater to avoid "recursing" the consumer.
  //
  MessageLoop::current()->PostTask(
      FROM_HERE,
      method_factory_.NewRunnableMethod(
          &URLRequestHttpJob::OnStartCompleted, OK));
}

void URLRequestHttpJob::ContinueWithCertificate(
    X509Certificate* client_cert) {
  DCHECK(transaction_.get());

  DCHECK(!response_info_) << "should not have a response yet";

  ResetTimer();

  // No matter what, we want to report our status as IO pending since we will
  // be notifying our consumer asynchronously via OnStartCompleted.
  SetStatus(URLRequestStatus(URLRequestStatus::IO_PENDING, 0));

  int rv = transaction_->RestartWithCertificate(client_cert, &start_callback_);
  if (rv == ERR_IO_PENDING)
    return;

  // The transaction started synchronously, but we need to notify the
  // URLRequest delegate via the message loop.
  MessageLoop::current()->PostTask(
      FROM_HERE,
      method_factory_.NewRunnableMethod(
          &URLRequestHttpJob::OnStartCompleted, rv));
}

void URLRequestHttpJob::ContinueDespiteLastError() {
  // If the transaction was destroyed, then the job was cancelled.
  if (!transaction_.get())
    return;

  DCHECK(!response_info_) << "should not have a response yet";

  ResetTimer();

  // No matter what, we want to report our status as IO pending since we will
  // be notifying our consumer asynchronously via OnStartCompleted.
  SetStatus(URLRequestStatus(URLRequestStatus::IO_PENDING, 0));

  int rv = transaction_->RestartIgnoringLastError(&start_callback_);
  if (rv == ERR_IO_PENDING)
    return;

  // The transaction started synchronously, but we need to notify the
  // URLRequest delegate via the message loop.
  MessageLoop::current()->PostTask(
      FROM_HERE,
      method_factory_.NewRunnableMethod(
          &URLRequestHttpJob::OnStartCompleted, rv));
}

bool URLRequestHttpJob::ShouldFixMismatchedContentLength(int rv) const {
  // Some servers send the body compressed, but specify the content length as
  // the uncompressed size.  Although this violates the HTTP spec we want to
  // support it (as IE and FireFox do), but *only* for an exact match.
  // See http://crbug.com/79694.
  if (rv == net::ERR_CONNECTION_CLOSED) {
    if (request_ && request_->response_headers()) {
      int64 expected_length = request_->response_headers()->GetContentLength();
      VLOG(1) << __FUNCTION__ << "() "
              << "\"" << request_->url().spec() << "\""
              << " content-length = " << expected_length
              << " pre total = " << prefilter_bytes_read()
              << " post total = " << postfilter_bytes_read();
      if (postfilter_bytes_read() == expected_length) {
        // Clear the error.
        return true;
      }
    }
  }
  return false;
}

bool URLRequestHttpJob::ReadRawData(IOBuffer* buf, int buf_size,
                                    int *bytes_read) {
  DCHECK_NE(buf_size, 0);
  DCHECK(bytes_read);
  DCHECK(!read_in_progress_);

  int rv = transaction_->Read(buf, buf_size, &read_callback_);

  if (ShouldFixMismatchedContentLength(rv))
    rv = 0;

  if (rv >= 0) {
    *bytes_read = rv;
    if (!rv)
      DoneWithRequest(FINISHED);
    return true;
  }

  if (rv == ERR_IO_PENDING) {
    read_in_progress_ = true;
    SetStatus(URLRequestStatus(URLRequestStatus::IO_PENDING, 0));
  } else {
    NotifyDone(URLRequestStatus(URLRequestStatus::FAILED, rv));
  }

  return false;
}

void URLRequestHttpJob::StopCaching() {
  if (transaction_.get())
    transaction_->StopCaching();
}

HostPortPair URLRequestHttpJob::GetSocketAddress() const {
  return response_info_ ? response_info_->socket_address : HostPortPair();
}

URLRequestHttpJob::~URLRequestHttpJob() {
  DCHECK(!sdch_test_control_ || !sdch_test_activated_);
  if (!is_cached_content_) {
    if (sdch_test_control_)
      RecordPacketStats(FilterContext::SDCH_EXPERIMENT_HOLDBACK);
    if (sdch_test_activated_)
      RecordPacketStats(FilterContext::SDCH_EXPERIMENT_DECODE);
  }
  // Make sure SDCH filters are told to emit histogram data while
  // filter_context_ is still alive.
  DestroyFilters();

  if (sdch_dictionary_url_.is_valid()) {
    // Prior to reaching the destructor, request_ has been set to a NULL
    // pointer, so request_->url() is no longer valid in the destructor, and we
    // use an alternate copy |request_info_.url|.
    SdchManager* manager = SdchManager::Global();
    // To be extra safe, since this is a "different time" from when we decided
    // to get the dictionary, we'll validate that an SdchManager is available.
    // At shutdown time, care is taken to be sure that we don't delete this
    // globally useful instance "too soon," so this check is just defensive
    // coding to assure that IF the system is shutting down, we don't have any
    // problem if the manager was deleted ahead of time.
    if (manager)  // Defensive programming.
      manager->FetchDictionary(request_info_.url, sdch_dictionary_url_);
  }
  DoneWithRequest(ABORTED);
}

void URLRequestHttpJob::RecordTimer() {
  if (request_creation_time_.is_null()) {
    NOTREACHED()
        << "The same transaction shouldn't start twice without new timing.";
    return;
  }

  base::TimeDelta to_start = base::Time::Now() - request_creation_time_;
  request_creation_time_ = base::Time();

  static const bool use_prefetch_histogram =
      base::FieldTrialList::TrialExists("Prefetch");

  UMA_HISTOGRAM_MEDIUM_TIMES("Net.HttpTimeToFirstByte", to_start);
  if (use_prefetch_histogram) {
    UMA_HISTOGRAM_MEDIUM_TIMES(
        base::FieldTrial::MakeName("Net.HttpTimeToFirstByte",
                                   "Prefetch"),
        to_start);
  }

  const bool is_prerender = !!(request_info_.load_flags & LOAD_PRERENDERING);
  if (is_prerender) {
    UMA_HISTOGRAM_MEDIUM_TIMES("Net.HttpTimeToFirstByte_Prerender",
                               to_start);
    if (use_prefetch_histogram) {
      UMA_HISTOGRAM_MEDIUM_TIMES(
          base::FieldTrial::MakeName("Net.HttpTimeToFirstByte_Prerender",
                                     "Prefetch"),
          to_start);
    }
  } else {
    UMA_HISTOGRAM_MEDIUM_TIMES("Net.HttpTimeToFirstByte_NonPrerender",
                               to_start);
    if (use_prefetch_histogram) {
      UMA_HISTOGRAM_MEDIUM_TIMES(
          base::FieldTrial::MakeName("Net.HttpTimeToFirstByte_NonPrerender",
                                     "Prefetch"),
          to_start);
    }
  }
}

void URLRequestHttpJob::ResetTimer() {
  if (!request_creation_time_.is_null()) {
    NOTREACHED()
        << "The timer was reset before it was recorded.";
    return;
  }
  request_creation_time_ = base::Time::Now();
}

void URLRequestHttpJob::UpdatePacketReadTimes() {
  if (!packet_timing_enabled_)
    return;

  if (filter_input_byte_count() <= bytes_observed_in_packets_) {
    DCHECK_EQ(filter_input_byte_count(), bytes_observed_in_packets_);
    return;  // No new bytes have arrived.
  }

  if (!bytes_observed_in_packets_)
    request_time_snapshot_ = request_ ? request_->request_time() : base::Time();

  final_packet_time_ = base::Time::Now();
  const size_t kTypicalPacketSize = 1430;
  while (filter_input_byte_count() > bytes_observed_in_packets_) {
    ++observed_packet_count_;
    if (packet_times_.size() < kSdchPacketHistogramCount) {
      packet_times_.push_back(final_packet_time_);
      DCHECK_EQ(static_cast<size_t>(observed_packet_count_),
                packet_times_.size());
    }
    bytes_observed_in_packets_ += kTypicalPacketSize;
  }
  // Since packets may not be full, we'll remember the number of bytes we've
  // accounted for in packets thus far.
  bytes_observed_in_packets_ = filter_input_byte_count();
}

void URLRequestHttpJob::RecordPacketStats(
    FilterContext::StatisticSelector statistic) const {
  if (!packet_timing_enabled_ || (final_packet_time_ == base::Time()))
    return;

  base::TimeDelta duration = final_packet_time_ - request_time_snapshot_;
  switch (statistic) {
    case FilterContext::SDCH_DECODE: {
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Network_Decode_Latency_F_a", duration,
                                  base::TimeDelta::FromMilliseconds(20),
                                  base::TimeDelta::FromMinutes(10), 100);
      UMA_HISTOGRAM_COUNTS_100("Sdch3.Network_Decode_Packets_b",
                               static_cast<int>(observed_packet_count_));
      UMA_HISTOGRAM_CUSTOM_COUNTS("Sdch3.Network_Decode_Bytes_Processed_b",
          static_cast<int>(bytes_observed_in_packets_), 500, 100000, 100);
      if (packet_times_.empty())
        return;
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Network_Decode_1st_To_Last_a",
                                  final_packet_time_ - packet_times_[0],
                                  base::TimeDelta::FromMilliseconds(20),
                                  base::TimeDelta::FromMinutes(10), 100);

      DCHECK_GT(kSdchPacketHistogramCount, 4u);
      if (packet_times_.size() <= 4)
        return;
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Network_Decode_1st_To_2nd_c",
                                  packet_times_[1] - packet_times_[0],
                                  base::TimeDelta::FromMilliseconds(1),
                                  base::TimeDelta::FromSeconds(10), 100);
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Network_Decode_2nd_To_3rd_c",
                                  packet_times_[2] - packet_times_[1],
                                  base::TimeDelta::FromMilliseconds(1),
                                  base::TimeDelta::FromSeconds(10), 100);
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Network_Decode_3rd_To_4th_c",
                                  packet_times_[3] - packet_times_[2],
                                  base::TimeDelta::FromMilliseconds(1),
                                  base::TimeDelta::FromSeconds(10), 100);
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Network_Decode_4th_To_5th_c",
                                  packet_times_[4] - packet_times_[3],
                                  base::TimeDelta::FromMilliseconds(1),
                                  base::TimeDelta::FromSeconds(10), 100);
      return;
    }
    case FilterContext::SDCH_PASSTHROUGH: {
      // Despite advertising a dictionary, we handled non-sdch compressed
      // content.
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Network_Pass-through_Latency_F_a",
                                  duration,
                                  base::TimeDelta::FromMilliseconds(20),
                                  base::TimeDelta::FromMinutes(10), 100);
      UMA_HISTOGRAM_COUNTS_100("Sdch3.Network_Pass-through_Packets_b",
                               observed_packet_count_);
      if (packet_times_.empty())
        return;
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Network_Pass-through_1st_To_Last_a",
                                  final_packet_time_ - packet_times_[0],
                                  base::TimeDelta::FromMilliseconds(20),
                                  base::TimeDelta::FromMinutes(10), 100);
      DCHECK_GT(kSdchPacketHistogramCount, 4u);
      if (packet_times_.size() <= 4)
        return;
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Network_Pass-through_1st_To_2nd_c",
                                  packet_times_[1] - packet_times_[0],
                                  base::TimeDelta::FromMilliseconds(1),
                                  base::TimeDelta::FromSeconds(10), 100);
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Network_Pass-through_2nd_To_3rd_c",
                                  packet_times_[2] - packet_times_[1],
                                  base::TimeDelta::FromMilliseconds(1),
                                  base::TimeDelta::FromSeconds(10), 100);
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Network_Pass-through_3rd_To_4th_c",
                                  packet_times_[3] - packet_times_[2],
                                  base::TimeDelta::FromMilliseconds(1),
                                  base::TimeDelta::FromSeconds(10), 100);
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Network_Pass-through_4th_To_5th_c",
                                  packet_times_[4] - packet_times_[3],
                                  base::TimeDelta::FromMilliseconds(1),
                                  base::TimeDelta::FromSeconds(10), 100);
      return;
    }

    case FilterContext::SDCH_EXPERIMENT_DECODE: {
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Experiment_Decode",
                                  duration,
                                  base::TimeDelta::FromMilliseconds(20),
                                  base::TimeDelta::FromMinutes(10), 100);
      // We already provided interpacket histograms above in the SDCH_DECODE
      // case, so we don't need them here.
      return;
    }
    case FilterContext::SDCH_EXPERIMENT_HOLDBACK: {
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Experiment_Holdback",
                                  duration,
                                  base::TimeDelta::FromMilliseconds(20),
                                  base::TimeDelta::FromMinutes(10), 100);
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Experiment_Holdback_1st_To_Last_a",
                                  final_packet_time_ - packet_times_[0],
                                  base::TimeDelta::FromMilliseconds(20),
                                  base::TimeDelta::FromMinutes(10), 100);

      DCHECK_GT(kSdchPacketHistogramCount, 4u);
      if (packet_times_.size() <= 4)
        return;
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Experiment_Holdback_1st_To_2nd_c",
                                  packet_times_[1] - packet_times_[0],
                                  base::TimeDelta::FromMilliseconds(1),
                                  base::TimeDelta::FromSeconds(10), 100);
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Experiment_Holdback_2nd_To_3rd_c",
                                  packet_times_[2] - packet_times_[1],
                                  base::TimeDelta::FromMilliseconds(1),
                                  base::TimeDelta::FromSeconds(10), 100);
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Experiment_Holdback_3rd_To_4th_c",
                                  packet_times_[3] - packet_times_[2],
                                  base::TimeDelta::FromMilliseconds(1),
                                  base::TimeDelta::FromSeconds(10), 100);
      UMA_HISTOGRAM_CLIPPED_TIMES("Sdch3.Experiment_Holdback_4th_To_5th_c",
                                  packet_times_[4] - packet_times_[3],
                                  base::TimeDelta::FromMilliseconds(1),
                                  base::TimeDelta::FromSeconds(10), 100);
      return;
    }
    default:
      NOTREACHED();
      return;
  }
}

// The common type of histogram we use for all compression-tracking histograms.
#define COMPRESSION_HISTOGRAM(name, sample) \
    do { \
      UMA_HISTOGRAM_CUSTOM_COUNTS("Net.Compress." name, sample, \
                                  500, 1000000, 100); \
    } while(0)

void URLRequestHttpJob::RecordCompressionHistograms() {
  DCHECK(request_);
  if (!request_)
    return;

  if (is_cached_content_ ||                // Don't record cached content
      !GetStatus().is_success() ||         // Don't record failed content
      !IsCompressibleContent() ||          // Only record compressible content
      !prefilter_bytes_read())       // Zero-byte responses aren't useful.
    return;

  // Miniature requests aren't really compressible.  Don't count them.
  const int kMinSize = 16;
  if (prefilter_bytes_read() < kMinSize)
    return;

  // Only record for http or https urls.
  bool is_http = request_->url().SchemeIs("http");
  bool is_https = request_->url().SchemeIs("https");
  if (!is_http && !is_https)
    return;

  int compressed_B = prefilter_bytes_read();
  int decompressed_B = postfilter_bytes_read();
  bool was_filtered = HasFilter();

  // We want to record how often downloaded resources are compressed.
  // But, we recognize that different protocols may have different
  // properties.  So, for each request, we'll put it into one of 3
  // groups:
  //      a) SSL resources
  //         Proxies cannot tamper with compression headers with SSL.
  //      b) Non-SSL, loaded-via-proxy resources
  //         In this case, we know a proxy might have interfered.
  //      c) Non-SSL, loaded-without-proxy resources
  //         In this case, we know there was no explicit proxy.  However,
  //         it is possible that a transparent proxy was still interfering.
  //
  // For each group, we record the same 3 histograms.

  if (is_https) {
    if (was_filtered) {
      COMPRESSION_HISTOGRAM("SSL.BytesBeforeCompression", compressed_B);
      COMPRESSION_HISTOGRAM("SSL.BytesAfterCompression", decompressed_B);
    } else {
      COMPRESSION_HISTOGRAM("SSL.ShouldHaveBeenCompressed", decompressed_B);
    }
    return;
  }

  if (request_->was_fetched_via_proxy()) {
    if (was_filtered) {
      COMPRESSION_HISTOGRAM("Proxy.BytesBeforeCompression", compressed_B);
      COMPRESSION_HISTOGRAM("Proxy.BytesAfterCompression", decompressed_B);
    } else {
      COMPRESSION_HISTOGRAM("Proxy.ShouldHaveBeenCompressed", decompressed_B);
    }
    return;
  }

  if (was_filtered) {
    COMPRESSION_HISTOGRAM("NoProxy.BytesBeforeCompression", compressed_B);
    COMPRESSION_HISTOGRAM("NoProxy.BytesAfterCompression", decompressed_B);
  } else {
    COMPRESSION_HISTOGRAM("NoProxy.ShouldHaveBeenCompressed", decompressed_B);
  }
}

bool URLRequestHttpJob::IsCompressibleContent() const {
  std::string mime_type;
  return GetMimeType(&mime_type) &&
      (IsSupportedJavascriptMimeType(mime_type.c_str()) ||
       IsSupportedNonImageMimeType(mime_type.c_str()));
}

void URLRequestHttpJob::RecordPerfHistograms(CompletionCause reason) {
  if (start_time_.is_null())
    return;

  base::TimeDelta total_time = base::TimeTicks::Now() - start_time_;
  UMA_HISTOGRAM_TIMES("Net.HttpJob.TotalTime", total_time);

  if (reason == FINISHED) {
    UMA_HISTOGRAM_TIMES("Net.HttpJob.TotalTimeSuccess", total_time);
  } else {
    UMA_HISTOGRAM_TIMES("Net.HttpJob.TotalTimeCancel", total_time);
  }

  static bool cache_experiment = false;
  if (!cache_experiment)
    cache_experiment = base::FieldTrialList::TrialExists("CacheListSize");
  if (cache_experiment) {
    UMA_HISTOGRAM_TIMES(
        base::FieldTrial::MakeName("Net.HttpJob.TotalTime", "CacheListSize"),
        total_time);
    if (reason == FINISHED) {
      UMA_HISTOGRAM_TIMES(
          base::FieldTrial::MakeName("Net.HttpJob.TotalTimeSuccess",
                                     "CacheListSize"),
          total_time);
    } else {
      UMA_HISTOGRAM_TIMES(
          base::FieldTrial::MakeName("Net.HttpJob.TotalTimeCancel",
                                     "CacheListSize"),
          total_time);
    }
  }

  start_time_ = base::TimeTicks();
}

void URLRequestHttpJob::DoneWithRequest(CompletionCause reason) {
  if (done_)
    return;
  done_ = true;

  RecordPerfHistograms(reason);
  if (reason == FINISHED)
    RecordCompressionHistograms();
}

}  // namespace net