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

Index: content/common/gpu/gpu_memory_buffer_factory_surface_texture.cc
diff --git a/content/common/gpu/gpu_memory_buffer_factory_surface_texture.cc b/content/common/gpu/gpu_memory_buffer_factory_surface_texture.cc
index 1b2c881f6aeb2e5420e57cd9e5bf68eb4672e543..be755302b22b6f3c633485d92fc48532f047aca8 100644
--- a/content/common/gpu/gpu_memory_buffer_factory_surface_texture.cc
+++ b/content/common/gpu/gpu_memory_buffer_factory_surface_texture.cc
@@ -51,6 +51,7 @@ GpuMemoryBufferFactorySurfaceTexture::CreateGpuMemoryBuffer(
     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
@@ -64,13 +65,9 @@ GpuMemoryBufferFactorySurfaceTexture::CreateGpuMemoryBuffer(
   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;
@@ -81,14 +78,11 @@ GpuMemoryBufferFactorySurfaceTexture::CreateGpuMemoryBuffer(
 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);
 }
@@ -104,8 +98,7 @@ GpuMemoryBufferFactorySurfaceTexture::CreateImageForGpuMemoryBuffer(
     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);