keep only one typedef for the native drawing context

skia/ext/bitmap_platform_device_skia.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 SKIA_EXT_BITMAP_PLATFORM_DEVICE_SKIA_H_
 #define SKIA_EXT_BITMAP_PLATFORM_DEVICE_SKIA_H_
 
 #include <stdint.h>
 
 #include "base/compiler_specific.h"
@@ skipping 28 matching lines @@
   // you should probably be using Create(). This may become private later if
   // we ever have to share state between some native drawing UI and Skia, like
   // the Windows and Mac versions of this class do.
   explicit BitmapPlatformDevice(const SkBitmap& other);
   ~BitmapPlatformDevice() override;
 
  protected:
   SkBaseDevice* onCreateDevice(const CreateInfo&, const SkPaint*) override;
 
  private:
-  PlatformSurface BeginPlatformPaint(const SkMatrix& transform,
-                                     const SkIRect& clip_bounds) override;
+  NativeDrawingContext BeginPlatformPaint(const SkMatrix& transform,
+                                          const SkIRect& clip_bounds) override;
 
   DISALLOW_COPY_AND_ASSIGN(BitmapPlatformDevice);
 
   friend class ScopedPlatformPaint;
 };
 
 }  // namespace skia
 
 #endif  // SKIA_EXT_BITMAP_PLATFORM_DEVICE_SKIA_H_