Adding instrumentation to locate the source of jankiness.

storage/browser/blob/local_file_stream_reader.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/blob/local_file_stream_reader.h"
 
 #include "base/files/file_util.h"
 #include "base/files/file_util_proxy.h"
 #include "base/location.h"
 #include "base/logging.h"
+#include "base/profiler/scoped_profile.h"
 #include "base/task_runner.h"
 #include "net/base/file_stream.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
 
 namespace storage {
 
 namespace {
 
 const int kOpenFlagsForRead = base::File::FLAG_OPEN |
@@ skipping 73 matching lines @@
       base::Bind(&LocalFileStreamReader::DidOpenFileStream,
                  weak_factory_.GetWeakPtr(),
                  callback));
   if (result != net::ERR_IO_PENDING)
     callback.Run(result);
 }
 
 void LocalFileStreamReader::DidOpenFileStream(
     const net::CompletionCallback& callback,
     int result) {
+  // TODO(vadimt): Remove ScopedProfile below once crbug.com/423948 is fixed.
+  tracked_objects::ScopedProfile tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "423948 LocalFileStreamReader::DidOpenFileStream"));
+
   if (result != net::OK) {
     callback.Run(result);
     return;
   }
   result = stream_impl_->Seek(
       base::File::FROM_BEGIN, initial_offset_,
       base::Bind(&LocalFileStreamReader::DidSeekFileStream,
                  weak_factory_.GetWeakPtr(),
                  callback));
   if (result != net::ERR_IO_PENDING) {
@@ skipping 46 matching lines @@
     return;
   }
   if (!VerifySnapshotTime(expected_modification_time_, file_info)) {
     callback.Run(net::ERR_UPLOAD_FILE_CHANGED);
     return;
   }
   callback.Run(file_info.size);
 }
 
 }  // namespace storage