cc: Add mailbox support to ResourceProvider write locks.

cc/raster/raster_buffer_provider.h

 // Copyright 2013 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 CC_RASTER_RASTER_BUFFER_PROVIDER_H_
 #define CC_RASTER_RASTER_BUFFER_PROVIDER_H_
 
 #include <stddef.h>
 
 #include "cc/playback/raster_source.h"
@@ skipping 35 matching lines @@
 
   // Acquire raster buffer.
   virtual std::unique_ptr<RasterBuffer> AcquireBufferForRaster(
       const Resource* resource,
       uint64_t resource_content_id,
       uint64_t previous_content_id) = 0;
 
   // Release raster buffer.
   virtual void ReleaseBufferForRaster(std::unique_ptr<RasterBuffer> buffer) = 0;
 
-  // Barrier to sync resources to the worker context.
-  virtual void OrderingBarrier() = 0;
+  // Used for syncing resources to the worker context. Returns false if barrier
+  // could not be established.
+  virtual bool OrderingBarrier() = 0;
 
   // Returns the format to use for the tiles.
   virtual ResourceFormat GetResourceFormat(bool must_support_alpha) const = 0;
 
   // Determine if the resource requires swizzling.
   virtual bool GetResourceRequiresSwizzle(bool must_support_alpha) const = 0;
 
   // Shutdown for doing cleanup.
   virtual void Shutdown() = 0;
 
  protected:
   // Check if resource format matches output format.
   static bool ResourceFormatRequiresSwizzle(ResourceFormat format);
 };
 
 }  // namespace cc
 
 #endif  // CC_RASTER_RASTER_BUFFER_PROVIDER_H_