zero-copy: Clarify to allocate/destroy GpuMemoryBuffer on any thread and use it on the main thread o

content/common/gpu/gpu_memory_buffer_factory_surface_texture.cc

 // Copyright 2014 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.
 
 #include "content/common/gpu/gpu_memory_buffer_factory_surface_texture.h"
 
 #include "content/common/android/surface_texture_manager.h"
 #include "ui/gl/android/surface_texture.h"
 #include "ui/gl/gl_image_surface_texture.h"
 
@@ skipping 87 matching lines @@
 }
 
 scoped_refptr<gfx::GLImage>
 GpuMemoryBufferFactorySurfaceTexture::CreateImageForGpuMemoryBuffer(
     const gfx::GpuMemoryBufferHandle& handle,
     const gfx::Size& size,
     gfx::GpuMemoryBuffer::Format format,
     unsigned internalformat,
     int client_id) {
   base::AutoLock lock(surface_textures_lock_);
-
+  DCHECK(thread_checker_.CalledOnValidThread());

[reveman, 2015/04/07 13:07:05]

ditto

[dshwang, 2015/04/07 14:04:26]

ditto

   DCHECK_EQ(handle.type, gfx::SURFACE_TEXTURE_BUFFER);
 
   SurfaceTextureMapKey key(handle.id, client_id);
   SurfaceTextureMap::iterator it = surface_textures_.find(key);
   if (it == surface_textures_.end())
     return scoped_refptr<gfx::GLImage>();
 
   scoped_refptr<gfx::GLImageSurfaceTexture> image(
       new gfx::GLImageSurfaceTexture(size));
   if (!image->Initialize(it->second.get()))
     return scoped_refptr<gfx::GLImage>();
 
   return image;
 }
 
 }  // namespace content