Use a shared thread for media operations.

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 <set>
 #include <string>
 #include <vector>
@@ skipping 254 matching lines @@
 
   // Get the GPU channel. Returns NULL if the channel is not established or
   // has been lost.
   GpuChannelHost* GetGpuChannel();
 
   // Returns a MessageLoopProxy instance corresponding to the message loop
   // of the thread on which file operations should be run. Must be called
   // on the renderer's main thread.
   scoped_refptr<base::MessageLoopProxy> GetFileThreadMessageLoopProxy();
 
+  // Returns a MessageLoopProxy instance corresponding to the message loop
+  // of the thread on which media operations should be run. Must be called
+  // on the renderer's main thread.
+  scoped_refptr<base::MessageLoopProxy> GetMediaThreadMessageLoopProxy();
+
   // Causes the idle handler to skip sending idle notifications
   // on the two next scheduled calls, so idle notifications are
   // not sent for at least one notification delay.
   void PostponeIdleNotification();
 
   // Returns a graphics context shared among all
   // RendererGpuVideoDecoderFactories, or NULL on error.  Context remains owned
   // by this class and must be null-tested before each use to detect context
   // loss.  The returned context is only valid on the compositor thread when
   // threaded compositing is enabled.
@@ skipping 150 matching lines @@
 
   // The channel from the renderer process to the GPU process.
   scoped_refptr<GpuChannelHost> gpu_channel_;
 
   // 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_;
 
+  // Thread for running multimedia operations (e.g., video decoding).
+  scoped_ptr<base::Thread> media_thread_;
+
   // Will point to appropriate MessageLoopProxy after initialization,
   // regardless of whether |compositor_thread_| is overriden.
   scoped_refptr<base::MessageLoopProxy> compositor_message_loop_proxy_;
 
   scoped_ptr<InputHandlerManager> input_handler_manager_;
   scoped_refptr<IPC::ForwardingMessageFilter> compositor_output_surface_filter_;
 
   class RendererContextProviderCommandBuffer;
   scoped_refptr<RendererContextProviderCommandBuffer>
       shared_contexts_main_thread_;
@@ skipping 10 matching lines @@
   scoped_ptr<media::AudioHardwareConfig> audio_hardware_config_;
 
   HistogramCustomizer histogram_customizer_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderThreadImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_THREAD_IMPL_H_