media: Make GpuMemoryBuffers VideoFrame copies asynchronous.

media/video/gpu_memory_buffer_video_frame_pool.h

 // Copyright 2015 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_VIDEO_GPU_MEMORY_BUFFER_VIDEO_FRAME_POOL_H_
 #define MEDIA_VIDEO_GPU_MEMORY_BUFFER_VIDEO_FRAME_POOL_H_
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/task_runner.h"
 #include "media/base/video_frame.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace media {
 class GpuVideoAcceleratorFactories;
 
 // Interface to a pool of GpuMemoryBuffers/textues/images that can be used to
 // transform software VideoFrames to VideoFrames backed by native textures.
 // The resources used by the VideoFrame created by the pool will be
 // automatically put back into the pool once the frame is destroyed.
 // The pool recycles resources to a void unnecessarily allocating and
 // destroying textures, images and GpuMemoryBuffer that could result
 // in a round trip to the browser/GPU process.
 class MEDIA_EXPORT GpuMemoryBufferVideoFramePool {
  public:
   GpuMemoryBufferVideoFramePool(
-      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
+      const scoped_refptr<base::SingleThreadTaskRunner>& media_task_runner,
+      const scoped_refptr<base::TaskRunner>& worker_task_runner,
       const scoped_refptr<GpuVideoAcceleratorFactories>& gpu_factories);
   ~GpuMemoryBufferVideoFramePool();
 
-  // Returns a new VideoFrame containing only mailboxes to native resources.
-  // The content of the returned object is copied from the software-allocated
+  // Callback used by MaybeCreateHardwareFrame to deliver a new VideoFrame
+  // after it has been copied to GpuMemoryBuffers.
+  typedef base::Callback<void(const scoped_refptr<VideoFrame>&)> FrameReadyCB;
+
+  // Calls |cb| on |media_worker_pool| with a new VideoFrame containing only
+  // mailboxes to native resources. |cb| will be destroyed on
+  // |media_worker_pool|.
+  // The content of the new object is copied from the software-allocated
   // |video_frame|.
   // If it's not possible to create a new hardware VideoFrame, |video_frame|
-  // itself will be returned.
-  scoped_refptr<VideoFrame> MaybeCreateHardwareFrame(
-      const scoped_refptr<VideoFrame>& video_frame);
+  // itself will passed to |cb|.
+  void MaybeCreateHardwareFrame(const scoped_refptr<VideoFrame>& video_frame,
+                                const FrameReadyCB& frame_ready_cb);
 
  private:
   class PoolImpl;
   scoped_refptr<PoolImpl> pool_impl_;
 
   DISALLOW_COPY_AND_ASSIGN(GpuMemoryBufferVideoFramePool);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_VIDEO_GPU_MEMORY_BUFFER_VIDEO_FRAME_POOL_H_