[NOT FOR REVIEW] Instrument net/ with trace events.

net/url_request/url_fetcher_core.cc

Index: net/url_request/url_fetcher_core.cc
diff --git a/net/url_request/url_fetcher_core.cc b/net/url_request/url_fetcher_core.cc
index ee1a3d8c83010938d4c6d10cedc3e69fd348384b..6d0992c258b5711be6f927bfb0b66d5e3c4e411b 100644
--- a/net/url_request/url_fetcher_core.cc
+++ b/net/url_request/url_fetcher_core.cc
@@ -15,6 +15,7 @@
 #include "base/single_thread_task_runner.h"
 #include "base/stl_util.h"
 #include "base/thread_task_runner_handle.h"
+#include "base/trace_event/trace_event.h"
 #include "base/tracked_objects.h"
 #include "net/base/elements_upload_data_stream.h"
 #include "net/base/io_buffer.h"
@@ -32,6 +33,8 @@
 #include "net/url_request/url_request_context_getter.h"
 #include "net/url_request/url_request_throttler_manager.h"
 
+#include "base/trace_event/trace_event.h"
+
 namespace {
 
 const int kBufferSize = 4096;
@@ -514,6 +517,7 @@ URLFetcherCore::~URLFetcherCore() {
 }
 
 void URLFetcherCore::StartOnIOThread() {
+  TRACE_EVENT0("net", "URLFetcherCore::StartOnIOThread");
   DCHECK(network_task_runner_->BelongsToCurrentThread());
 
   if (!response_writer_)
@@ -746,6 +750,7 @@ void URLFetcherCore::DidFinishWriting(int result) {
 }
 
 void URLFetcherCore::RetryOrCompleteUrlFetch() {
+  TRACE_EVENT0("net", "net::URLFetcherCore::RetryOrCompleteUrlFetch");
   DCHECK(network_task_runner_->BelongsToCurrentThread());
   base::TimeDelta backoff_delay;