keep only one typedef for the native drawing context

skia/ext/bitmap_platform_device_skia.cc

 // 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.
 
 #include "skia/ext/bitmap_platform_device_skia.h"
 #include "skia/ext/platform_canvas.h"
 
 namespace skia {
 
 BitmapPlatformDevice* BitmapPlatformDevice::Create(int width, int height,
@@ skipping 31 matching lines @@
 BitmapPlatformDevice::~BitmapPlatformDevice() {
 }
 
 SkBaseDevice* BitmapPlatformDevice::onCreateDevice(const CreateInfo& info,
                                                    const SkPaint*) {
   SkASSERT(info.fInfo.colorType() == kN32_SkColorType);
   return BitmapPlatformDevice::Create(info.fInfo.width(), info.fInfo.height(),
                                       info.fInfo.isOpaque());
 }
 
-PlatformSurface BitmapPlatformDevice::BeginPlatformPaint(const SkMatrix& transform,
-                                                         const SkIRect& clip_bounds) {
+NativeDrawingContext BitmapPlatformDevice::BeginPlatformPaint(
+    const SkMatrix& transform,
+    const SkIRect& clip_bounds) {
   // TODO(zhenghao): What should we return? The ptr to the address of the
   // pixels? Maybe this won't be called at all.
   SkPixmap pixmap;
   return accessPixels(&pixmap) ? pixmap.writable_addr() : nullptr;
 }
 
 // PlatformCanvas impl
 
 SkCanvas* CreatePlatformCanvas(int width, int height, bool is_opaque,
                                uint8_t* data, OnFailureType failureType) {
   sk_sp<SkBaseDevice> dev(
       BitmapPlatformDevice::Create(width, height, is_opaque, data));
   return CreateCanvas(dev, failureType);
 }
 
 }  // namespace skia