Instrumenting callbacks of HttpNetworkTransaction to locate the source of jankiness

chrome/browser/devtools/devtools_network_transaction.cc

 // Copyright 2014 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/devtools/devtools_network_transaction.h"
 
+#include "base/profiler/scoped_tracker.h"
 #include "chrome/browser/devtools/devtools_network_controller.h"
 #include "chrome/browser/devtools/devtools_network_interceptor.h"
 #include "net/base/net_errors.h"
 #include "net/base/upload_progress.h"
 #include "net/http/http_network_transaction.h"
 #include "net/http/http_request_info.h"
 
 namespace {
 
 // Keep in sync with kDevToolsRequestInitiator and
@@ skipping 30 matching lines @@
   if (callback_type_ == START)
     throttled_byte_count_ += network_transaction_->GetTotalReceivedBytes();
   if (result > 0)
     throttled_byte_count_ += result;
 
   if (interceptor_)
     interceptor_->ThrottleTransaction(this, callback_type_ == START);
 }
 
 void DevToolsNetworkTransaction::OnCallback(int rv) {
+  // TODO(vadimt): Remove ScopedTracker below once crbug.com/424359 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "424359 DevToolsNetworkTransaction::OnCallback"));
+
   if (failed_)
     return;
   DCHECK(!callback_.is_null());
   if (callback_type_ == START || callback_type_ == READ) {
     if (interceptor_ && interceptor_->ShouldThrottle(this)) {
       Throttle(rv);
       return;
     }
   }
   net::CompletionCallback callback = callback_;
@@ skipping 202 matching lines @@
 }
 
 void DevToolsNetworkTransaction::FireThrottledCallback() {
   DCHECK(!callback_.is_null());
   DCHECK(callback_type_ == READ || callback_type_ == START);
   net::CompletionCallback callback = callback_;
   callback_.Reset();
   callback_type_ = NONE;
   callback.Run(throttled_result_);
 }