Adding instrumentation to locate the source of jankiness.

storage/browser/fileapi/local_file_stream_writer.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 "storage/browser/fileapi/local_file_stream_writer.h"
 
 #include "base/callback.h"
 #include "base/message_loop/message_loop.h"
+#include "base/profiler/scoped_profile.h"
 #include "net/base/file_stream.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
 
 namespace storage {
 
 namespace {
 
 const int kOpenFlagsForWrite = base::File::FLAG_OPEN |
                                base::File::FLAG_WRITE |
@@ skipping 99 matching lines @@
                             base::Bind(&LocalFileStreamWriter::DidOpen,
                                        weak_factory_.GetWeakPtr(),
                                        error_callback,
                                        main_operation));
 }
 
 void LocalFileStreamWriter::DidOpen(
     const net::CompletionCallback& error_callback,
     const base::Closure& main_operation,
     int result) {
+  // TODO(vadimt): Remove ScopedProfile below once crbug.com/423948 is fixed.
+  tracked_objects::ScopedProfile tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "423948 LocalFileStreamWriter::DidOpen"));
+
   DCHECK(has_pending_operation_);
   DCHECK(stream_impl_.get());
 
   if (CancelIfRequested())
     return;
 
   if (result != net::OK) {
     has_pending_operation_ = false;
     stream_impl_.reset(NULL);
     error_callback.Run(result);
@@ skipping 110 matching lines @@
     return false;
 
   net::CompletionCallback pending_cancel = cancel_callback_;
   has_pending_operation_ = false;
   cancel_callback_.Reset();
   pending_cancel.Run(net::OK);
   return true;
 }
 
 }  // namespace storage