[Sync] Move //sync to //components/sync.

There are a bunch of subfolder reorganizations going along with this:

- engine/ -> engine_impl/
- sessions/ -> sessions_impl/
- util/ -> base/
- internal_api/public/base/ -> base/
- internal_api/public/sessions/ -> sessions/
- internal_api/public/engine/ -> engine/
- internal_api/public/events/ -> engine/events/
- internal_api/public/util/ -> base/
- internal_api/public/ -> core/
- internal_api/ -> core_impl/

This change was generated using the following script:
http://pastebin.com/vVAkRCkh

Because this patch is so large, some review was done in split CLs:

Manual changes: http://crrev.com/2155763002
Sync internal changes: http://crrev.com/2156693002
Sync external changes: http://crrev.com/2148293004

This is a minimal change to support file movement; it doesn't do
anything like merging sync_unit_tests into component_unit_tests,
which will be done in a followup.

The gyp files are not sorted because they're all going to be removed
very soon anyways.

BUG=626114
[email protected], [email protected]
TBR=jam

Review URL: https://codereview.chromium.org/2130453004 .

Cr-Commit-Position: refs/heads/master@{#408497}
diff --git a/components/gcm_driver/gcm_channel_status_request.cc b/components/gcm_driver/gcm_channel_status_request.cc
index 8cb9e4c..6a73d85 100644
--- a/components/gcm_driver/gcm_channel_status_request.cc
+++ b/components/gcm_driver/gcm_channel_status_request.cc
@@ -9,12 +9,12 @@
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/gcm_driver/gcm_backoff_policy.h"
+#include "components/sync/protocol/experiment_status.pb.h"
 #include "net/base/escape.h"
 #include "net/base/load_flags.h"
 #include "net/http/http_status_code.h"
 #include "net/url_request/url_fetcher.h"
 #include "net/url_request/url_request_status.h"
-#include "sync/protocol/experiment_status.pb.h"
 #include "url/gurl.h"
 
 namespace gcm {