cc: Add mailbox support to ResourceProvider write locks.

cc/test/fake_raster_buffer_provider.cc

 // Copyright 2016 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 "cc/test/fake_raster_buffer_provider.h"
 
 namespace cc {
 
 FakeRasterBufferProviderImpl::FakeRasterBufferProviderImpl() {}
 
 FakeRasterBufferProviderImpl::~FakeRasterBufferProviderImpl() {}
 
 std::unique_ptr<RasterBuffer>
 FakeRasterBufferProviderImpl::AcquireBufferForRaster(
     const Resource* resource,
     uint64_t resource_content_id,
     uint64_t previous_content_id) {
   return nullptr;
 }
 
 void FakeRasterBufferProviderImpl::ReleaseBufferForRaster(
     std::unique_ptr<RasterBuffer> buffer) {}
 
-void FakeRasterBufferProviderImpl::OrderingBarrier() {}
+bool FakeRasterBufferProviderImpl::OrderingBarrier() {
+  return true;
+}
 
 ResourceFormat FakeRasterBufferProviderImpl::GetResourceFormat(
     bool must_support_alpha) const {
   return ResourceFormat::RGBA_8888;
 }
 
 bool FakeRasterBufferProviderImpl::GetResourceRequiresSwizzle(
     bool must_support_alpha) const {
   return ResourceFormatRequiresSwizzle(GetResourceFormat(must_support_alpha));
 }
 
 void FakeRasterBufferProviderImpl::Shutdown() {}
 
 }  // namespace cc