Adding instrumentation to locate the source of jankiness.

net/url_request/url_request_http_job.cc

Index: net/url_request/url_request_http_job.cc
diff --git a/net/url_request/url_request_http_job.cc b/net/url_request/url_request_http_job.cc
index 68858c147586fc902d58c50f946829c46bf543e1..084165bbc783d9084fe20f31fb84661478176980 100644
--- a/net/url_request/url_request_http_job.cc
+++ b/net/url_request/url_request_http_job.cc
@@ -1020,6 +1020,11 @@ void URLRequestHttpJob::SetExtraRequestHeaders(
 }
 
 LoadState URLRequestHttpJob::GetLoadState() const {
+  // TODO(pkasting): Remove ScopedTracker below once crbug.com/455952 is
+  // fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "455952 URLRequestHttpJob::GetLoadState"));
   return transaction_.get() ?
       transaction_->GetLoadState() : LOAD_STATE_IDLE;
 }