Adding instrumentation to locate the source of jankiness.

chrome/browser/download/download_resource_throttle.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/download/download_resource_throttle.h"
 
 #include "base/bind.h"
+#include "base/profiler/scoped_tracker.h"
 #include "chrome/browser/download/download_stats.h"
 #include "content/public/browser/resource_controller.h"
 
 DownloadResourceThrottle::DownloadResourceThrottle(
     DownloadRequestLimiter* limiter,
     int render_process_id,
     int render_view_id,
     const GURL& url,
     const std::string& request_method)
     : querying_limiter_(true),
@@ skipping 14 matching lines @@
 void DownloadResourceThrottle::WillStartRequest(bool* defer) {
   WillDownload(defer);
 }
 
 void DownloadResourceThrottle::WillRedirectRequest(const GURL& new_url,
                                                    bool* defer) {
   WillDownload(defer);
 }
 
 void DownloadResourceThrottle::WillProcessResponse(bool* defer) {
+  // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "422516 DownloadResourceThrottle::WillProcessResponse"));
+
   WillDownload(defer);
 }
 
 const char* DownloadResourceThrottle::GetNameForLogging() const {
   return "DownloadResourceThrottle";
 }
 
 void DownloadResourceThrottle::WillDownload(bool* defer) {
   DCHECK(!request_deferred_);
 
@@ skipping 22 matching lines @@
 
   if (request_deferred_) {
     request_deferred_ = false;
     if (allow) {
       controller()->Resume();
     } else {
       controller()->Cancel();
     }
   }
 }