Adding instrumentation to locate the source of jankiness.

net/url_request/sdch_dictionary_fetcher.cc

Index: net/url_request/sdch_dictionary_fetcher.cc
diff --git a/net/url_request/sdch_dictionary_fetcher.cc b/net/url_request/sdch_dictionary_fetcher.cc
index 580619312c8ef646ef9d469b4fccdb1691c60dd6..0e15837424155ffc7040f24e6aaa0515cb05810e 100644
--- a/net/url_request/sdch_dictionary_fetcher.cc
+++ b/net/url_request/sdch_dictionary_fetcher.cc
@@ -9,6 +9,7 @@
 #include "base/auto_reset.h"
 #include "base/bind.h"
 #include "base/compiler_specific.h"
+#include "base/profiler/scoped_tracker.h"
 #include "base/thread_task_runner_handle.h"
 #include "net/base/load_flags.h"
 #include "net/url_request/url_request_context.h"
@@ -81,6 +82,11 @@ void SdchDictionaryFetcher::Cancel() {
 }
 
 void SdchDictionaryFetcher::OnResponseStarted(URLRequest* request) {
+  // TODO(vadimt): Remove ScopedTracker below once crbug.com/423948 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "423948 SdchDictionaryFetcher::OnResponseStarted"));
+
   DCHECK(CalledOnValidThread());
   DCHECK_EQ(request, current_request_.get());
   DCHECK_EQ(next_state_, STATE_REQUEST_STARTED);
@@ -99,6 +105,11 @@ void SdchDictionaryFetcher::OnResponseStarted(URLRequest* request) {
 
 void SdchDictionaryFetcher::OnReadCompleted(URLRequest* request,
                                             int bytes_read) {
+  // TODO(vadimt): Remove ScopedTracker below once crbug.com/423948 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "423948 SdchDictionaryFetcher::OnReadCompleted"));
+
   DCHECK(CalledOnValidThread());
   DCHECK_EQ(request, current_request_.get());
   DCHECK_EQ(next_state_, STATE_REQUEST_READING);