keep only one typedef for the native drawing context

skia/ext/bitmap_platform_device_skia.cc

Index: skia/ext/bitmap_platform_device_skia.cc
diff --git a/skia/ext/bitmap_platform_device_skia.cc b/skia/ext/bitmap_platform_device_skia.cc
index 93d8f7d8184c760f4f004cebfec1f0586d8a4288..77957af919be5e3f18b35026464fa0e3b91b54fe 100644
--- a/skia/ext/bitmap_platform_device_skia.cc
+++ b/skia/ext/bitmap_platform_device_skia.cc
@@ -49,8 +49,9 @@ SkBaseDevice* BitmapPlatformDevice::onCreateDevice(const CreateInfo& info,
                                       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;