Add skia::RefPtr class to wrap ref counted classes from Skia.

skia/ext/bitmap_platform_device_mac.h

Index: skia/ext/bitmap_platform_device_mac.h
diff --git a/skia/ext/bitmap_platform_device_mac.h b/skia/ext/bitmap_platform_device_mac.h
index 0d00a0abb5d4ca0707f545a776ed7ec852048361..17c7d7121080f7043fe4a83376e3771aac84ab2b 100644
--- a/skia/ext/bitmap_platform_device_mac.h
+++ b/skia/ext/bitmap_platform_device_mac.h
@@ -8,6 +8,7 @@
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "skia/ext/platform_device.h"
+#include "skia/ext/refptr.h"
 
 namespace skia {
 
@@ -76,9 +77,8 @@ class SK_API BitmapPlatformDevice : public SkDevice, public PlatformDevice {
                                              int height, bool isOpaque,
                                              Usage usage) OVERRIDE;
 
-  // Data associated with this device, guaranteed non-null. We hold a reference
-  // to this object.
-  BitmapPlatformDeviceData* data_;
+  // Data associated with this device, guaranteed non-null.
+  skia::RefPtr<BitmapPlatformDeviceData> data_;
 
   DISALLOW_COPY_AND_ASSIGN(BitmapPlatformDevice);
 };