Use enum instead of string in MessageLoopFactory::GetMessageLoop*

media/filters/gpu_video_decoder.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 MEDIA_FILTERS_GPU_VIDEO_DECODER_H_
 #define MEDIA_FILTERS_GPU_VIDEO_DECODER_H_
 
 #include <deque>
 #include <list>
 #include <map>
@@ skipping 38 matching lines @@
 
     // Allocate & return a shared memory segment.  Caller is responsible for
     // Close()ing the returned pointer.
     virtual base::SharedMemory* CreateSharedMemory(size_t size) = 0;
 
    protected:
     friend class base::RefCountedThreadSafe<Factories>;
     virtual ~Factories();
   };
 
-  GpuVideoDecoder(MessageLoop* message_loop,
-                  MessageLoop* vda_loop,
+  typedef base::Callback<
+      scoped_refptr<base::MessageLoopProxy>()> MessageLoopFactoryCB;
+  GpuVideoDecoder(const MessageLoopFactoryCB& message_loop_factory_cb,
+                  const scoped_refptr<base::MessageLoopProxy>& vda_loop_proxy,
                   const scoped_refptr<Factories>& factories);
 
   // VideoDecoder implementation.
   virtual void Initialize(const scoped_refptr<DemuxerStream>& stream,
                           const PipelineStatusCB& status_cb,
                           const StatisticsCB& statistics_cb) OVERRIDE;
   virtual void Read(const ReadCB& read_cb) OVERRIDE;
   virtual void Reset(const base::Closure& closure) OVERRIDE;
   virtual void Stop(const base::Closure& closure) OVERRIDE;
   virtual bool HasAlpha() const OVERRIDE;
@@ skipping 71 matching lines @@
   SHMBuffer* GetSHM(size_t min_size);
 
   // Return a shared-memory segment to the available pool.
   void PutSHM(SHMBuffer* shm_buffer);
 
   StatisticsCB statistics_cb_;
 
   // Pointer to the demuxer stream that will feed us compressed buffers.
   scoped_refptr<DemuxerStream> demuxer_stream_;
 
+  // This is !is_null() iff Initialize() hasn't been called.
+  MessageLoopFactoryCB message_loop_factory_cb_;
+
   // MessageLoop on which to fire callbacks and trampoline calls to this class
   // if they arrive on other loops.
   scoped_refptr<base::MessageLoopProxy> gvd_loop_proxy_;
 
   // Message loop on which to makes all calls to vda_.  (beware this loop may be
   // paused during the Pause/Flush/Stop dance PipelineImpl::Stop() goes
   // through).
   scoped_refptr<base::MessageLoopProxy> vda_loop_proxy_;
 
   scoped_refptr<Factories> factories_;
@@ skipping 54 matching lines @@
 
   // Indicates decoding error occurred.
   bool error_occured_;
 
   DISALLOW_COPY_AND_ASSIGN(GpuVideoDecoder);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_GPU_VIDEO_DECODER_H_