Make DrawingBuffer and Canvas2DLayerBridge be cc::TextureLayerClients.

cc/blink/web_external_bitmap_impl.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 "cc/blink/web_external_bitmap_impl.h"
-
-#include <stdint.h>
-
-#include "cc/resources/shared_bitmap.h"
-
-namespace cc_blink {
-
-namespace {
-
-SharedBitmapAllocationFunction g_memory_allocator;
-
-}  // namespace
-
-void SetSharedBitmapAllocationFunction(
-    SharedBitmapAllocationFunction allocator) {
-  g_memory_allocator = allocator;
-}
-
-WebExternalBitmapImpl::WebExternalBitmapImpl() {
-}
-
-WebExternalBitmapImpl::~WebExternalBitmapImpl() {
-}
-
-void WebExternalBitmapImpl::setSize(blink::WebSize size) {
-  if (size != size_) {
-    shared_bitmap_ = g_memory_allocator(gfx::Size(size));
-    size_ = size;
-  }
-}
-
-blink::WebSize WebExternalBitmapImpl::size() {
-  return size_;
-}
-
-uint8_t* WebExternalBitmapImpl::pixels() {
-  if (!shared_bitmap_) {
-    // crbug.com/520417: not sure why a non-null WebExternalBitmap is
-    // being passed to prepareMailbox when the shared_bitmap_ is null.
-    // Best hypothesis is that the bitmap is zero-sized.
-    DCHECK(size_.isEmpty());
-    return nullptr;
-  }
-  return shared_bitmap_->pixels();
-}
-
-}  // namespace cc_blink