net: Use stl utilities from the base namespace

The utilities in base/stl_util.h have been moved from the global
into the base namespace. This patch updates the call sites accordingly.

No functional changes.

BUG=636301

Review-Url: https://codereview.chromium.org/2229393003
Cr-Commit-Position: refs/heads/master@{#411615}
diff --git a/net/http/http_network_session.cc b/net/http/http_network_session.cc
index 8fe401c..fe66a8d 100644
--- a/net/http/http_network_session.cc
+++ b/net/http/http_network_session.cc
@@ -246,18 +246,18 @@
 }
 
 HttpNetworkSession::~HttpNetworkSession() {
-  STLDeleteElements(&response_drainers_);
+  base::STLDeleteElements(&response_drainers_);
   spdy_session_pool_.CloseAllSessions();
 }
 
 void HttpNetworkSession::AddResponseDrainer(HttpResponseBodyDrainer* drainer) {
-  DCHECK(!ContainsKey(response_drainers_, drainer));
+  DCHECK(!base::ContainsKey(response_drainers_, drainer));
   response_drainers_.insert(drainer);
 }
 
 void HttpNetworkSession::RemoveResponseDrainer(
     HttpResponseBodyDrainer* drainer) {
-  DCHECK(ContainsKey(response_drainers_, drainer));
+  DCHECK(base::ContainsKey(response_drainers_, drainer));
   response_drainers_.erase(drainer);
 }