compositor worker: Use a WebThread for the compositor thread.

content/renderer/render_thread_impl.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_RENDERER_RENDER_THREAD_IMPL_H_
 #define CONTENT_RENDERER_RENDER_THREAD_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 582 matching lines @@
 
   // The message loop of the renderer main thread.
   // This message loop should be destructed before the RenderThreadImpl
   // shuts down Blink.
   scoped_ptr<base::MessageLoop> main_message_loop_;
 
   // A lazily initiated thread on which file operations are run.
   scoped_ptr<base::Thread> file_thread_;
 
   // May be null if overridden by ContentRendererClient.
-  scoped_ptr<base::Thread> compositor_thread_;
+  scoped_ptr<scheduler::WebThreadBase> compositor_thread_;
 
   // Utility class to provide GPU functionalities to media.
   scoped_ptr<content::RendererGpuVideoAcceleratorFactories> gpu_factories_;
 
   // Thread for running multimedia operations (e.g., video decoding).
   scoped_ptr<base::Thread> media_thread_;
 
   // Will point to appropriate task runner after initialization,
   // regardless of whether |compositor_thread_| is overriden.
   scoped_refptr<base::SingleThreadTaskRunner> compositor_task_runner_;
@@ skipping 84 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(RenderThreadImpl);
 };
 
 #if defined(COMPILER_MSVC)
 #pragma warning(pop)
 #endif
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_THREAD_IMPL_H_