Revert of Delete Mac & Cairo skia::BitmapPlatformDevice impls

skia/ext/bitmap_platform_device_skia.h

Index: skia/ext/bitmap_platform_device_skia.h
diff --git a/skia/ext/bitmap_platform_device_skia.h b/skia/ext/bitmap_platform_device_skia.h
index 42a3be1d3422f194d2beab63e2701914d0dbd020..024064f4dac3c1914ae7141f840603ed5f1ae294 100644
--- a/skia/ext/bitmap_platform_device_skia.h
+++ b/skia/ext/bitmap_platform_device_skia.h
@@ -21,21 +21,15 @@
 // shared memory between the renderer and the main process at least. In this
 // case we'll probably create the buffer from a precreated region of memory.
 // -----------------------------------------------------------------------------
-class BitmapPlatformDevice final : public SkBitmapDevice,
-                                   public PlatformDevice {
+class BitmapPlatformDevice : public SkBitmapDevice, public PlatformDevice {
  public:
   // Construct a BitmapPlatformDevice. |is_opaque| should be set if the caller
-  // knows the bitmap will be completely opaque and allows some optimizations
-  // (the bitmap is not initialized to 0 when is_opaque == true).
+  // knows the bitmap will be completely opaque and allows some optimizations.
+  // The bitmap is not initialized.
   static BitmapPlatformDevice* Create(int width, int height, bool is_opaque);
 
-  // This doesn't take ownership of |data|. If |data| is null and |is_opaque|
-  // is false, the bitmap is initialized to 0.
-  //
-  // Note: historicaly, BitmapPlatformDevice impls have had diverging
-  // initialization behavior for null |data| (Cairo used to initialize, while
-  // the others did not).  For now we stick to the more conservative Cairo
-  // behavior.
+  // This doesn't take ownership of |data|. If |data| is null, the bitmap
+  // is not initialized to 0.
   static BitmapPlatformDevice* Create(int width, int height, bool is_opaque,
                                       uint8_t* data);
 
@@ -50,6 +44,9 @@
   SkBaseDevice* onCreateDevice(const CreateInfo&, const SkPaint*) override;
 
  private:
+  NativeDrawingContext BeginPlatformPaint(const SkMatrix& transform,
+                                          const SkIRect& clip_bounds) override;
+
   DISALLOW_COPY_AND_ASSIGN(BitmapPlatformDevice);
 };