Revert of Delete Mac & Cairo skia::BitmapPlatformDevice impls

skia/ext/bitmap_platform_device_win.h

Index: skia/ext/bitmap_platform_device_win.h
diff --git a/skia/ext/bitmap_platform_device_win.h b/skia/ext/bitmap_platform_device_win.h
index 6f359e2caf7aa5310c9b836423fe30fdeba69320..82f17ff3438a1989f74474d534292c287df9542a 100644
--- a/skia/ext/bitmap_platform_device_win.h
+++ b/skia/ext/bitmap_platform_device_win.h
@@ -17,8 +17,8 @@
 // format that Skia supports and can then use this to draw ClearType into, etc.
 // This pixel data is provided to the bitmap that the device contains so that it
 // can be shared.
-class SK_API BitmapPlatformDevice final : public SkBitmapDevice,
-                                          public PlatformDevice {
+class SK_API BitmapPlatformDevice : public SkBitmapDevice,
+                                    public PlatformDevice {
  public:
   // Factory function. is_opaque should be set if the caller knows the bitmap
   // will be completely opaque and allows some optimizations.