Use a shared thread for media operations.

content/shell/renderer/webkit_test_runner.h

 // 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.
 
 #ifndef CONTENT_SHELL_WEBKIT_TEST_RUNNER_H_
 #define CONTENT_SHELL_WEBKIT_TEST_RUNNER_H_
 
 #include <vector>
 
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/threading/thread.h"
 #include "content/public/renderer/render_view_observer.h"
 #include "content/public/renderer/render_view_observer_tracker.h"
 #include "content/shell/common/shell_test_configuration.h"
 #include "third_party/WebKit/Tools/DumpRenderTree/chromium/TestRunner/public/WebPreferences.h"
 #include "third_party/WebKit/Tools/DumpRenderTree/chromium/TestRunner/public/WebTestDelegate.h"
 #include "v8/include/v8.h"
 
 class SkCanvas;
 
 namespace WebKit {
@@ skipping 108 matching lines @@
 
   std::vector<int> routing_ids_;
   std::vector<std::vector<std::string> > session_histories_;
   std::vector<unsigned> current_entry_indexes_;
 
   bool is_main_window_;
 
   bool focus_on_next_commit_;
 
   scoped_ptr<webkit_glue::TestMediaStreamClient> test_media_stream_client_;
+  base::Thread media_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(WebKitTestRunner);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_SHELL_WEBKIT_TEST_RUNNER_H_