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 33 matching lines @@
 }
 
 gfx::GpuMemoryBufferHandle
 GpuMemoryBufferFactorySurfaceTexture::CreateGpuMemoryBuffer(
     gfx::GpuMemoryBufferId id,
     const gfx::Size& size,
     gfx::GpuMemoryBuffer::Format format,
     gfx::GpuMemoryBuffer::Usage usage,
     int client_id,
     gfx::PluginWindowHandle surface_handle) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   // Note: this needs to be 0 as the surface texture implemenation will take
   // ownership of the texture and call glDeleteTextures when the GPU service
   // attaches the surface texture to a real texture id. glDeleteTextures
   // silently ignores 0.
   const int kDummyTextureId = 0;
   scoped_refptr<gfx::SurfaceTexture> surface_texture =
       gfx::SurfaceTexture::Create(kDummyTextureId);
   if (!surface_texture.get())
     return gfx::GpuMemoryBufferHandle();
 
   SurfaceTextureManager::GetInstance()->RegisterSurfaceTexture(
       id, client_id, surface_texture.get());
 
-  {
-    base::AutoLock lock(surface_textures_lock_);
-
-    SurfaceTextureMapKey key(id, client_id);
-    DCHECK(surface_textures_.find(key) == surface_textures_.end());
-    surface_textures_[key] = surface_texture;
-  }
+  SurfaceTextureMapKey key(id, client_id);
+  DCHECK(surface_textures_.find(key) == surface_textures_.end());
+  surface_textures_[key] = surface_texture;
 
   gfx::GpuMemoryBufferHandle handle;
   handle.type = gfx::SURFACE_TEXTURE_BUFFER;
   handle.id = id;
   return handle;
 }
 
 void GpuMemoryBufferFactorySurfaceTexture::DestroyGpuMemoryBuffer(
     gfx::GpuMemoryBufferId id,
     int client_id) {
-  {
-    base::AutoLock lock(surface_textures_lock_);
-
-    SurfaceTextureMapKey key(id, client_id);
-    SurfaceTextureMap::iterator it = surface_textures_.find(key);
-    if (it != surface_textures_.end())
-      surface_textures_.erase(it);
-  }
+  DCHECK(thread_checker_.CalledOnValidThread());
+  SurfaceTextureMapKey key(id, client_id);
+  SurfaceTextureMap::iterator it = surface_textures_.find(key);
+  if (it != surface_textures_.end())
+    surface_textures_.erase(it);
 
   SurfaceTextureManager::GetInstance()->UnregisterSurfaceTexture(id, client_id);
 }
 
 gpu::ImageFactory* GpuMemoryBufferFactorySurfaceTexture::AsImageFactory() {
   return this;
 }
 
 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());
   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