Adding instrumentation to locate the source of jankiness.

content/child/web_data_consumer_handle_impl.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 "content/child/web_data_consumer_handle_impl.h"
 
 #include <limits>
 #include "base/bind.h"
 #include "base/logging.h"
+#include "base/profiler/scoped_tracker.h"
 #include "third_party/mojo/src/mojo/public/c/system/types.h"
 
 namespace content {
 
 typedef blink::WebDataConsumerHandle::Result Result;
 
 WebDataConsumerHandleImpl::WebDataConsumerHandleImpl(Handle handle)
     : handle_(handle.Pass()), client_(nullptr) {}
 
 WebDataConsumerHandleImpl::~WebDataConsumerHandleImpl() {}
@@ skipping 82 matching lines @@
       }
       return ShouldWait;
     case MOJO_RESULT_RESOURCE_EXHAUSTED:
       return ResourceExhausted;
     default:
       return UnexpectedError;
   }
 }
 
 void WebDataConsumerHandleImpl::OnHandleGotReadable(MojoResult) {
+  // TODO(pkasting): Remove ScopedTracker below once crbug.com/455434 is
+  // fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "455434 WebDataConsumerHandleImpl::OnHandleGotReadable"));
   DCHECK(client_);
   client_->didGetReadable();
 }
 
 }  // namespace content