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

skia/ext/platform_canvas.h

Index: skia/ext/platform_canvas.h
diff --git a/skia/ext/platform_canvas.h b/skia/ext/platform_canvas.h
index c83e6bf69f6ad07676848a9e4044064a5de87bdb..d906012d0a18d6bfc8e0a58a436a9c47360daee1 100644
--- a/skia/ext/platform_canvas.h
+++ b/skia/ext/platform_canvas.h
@@ -9,6 +9,7 @@
 // to get the surface type.
 #include "base/basictypes.h"
 #include "skia/ext/platform_device.h"
+#include "skia/ext/refptr.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 
 namespace skia {
@@ -71,8 +72,8 @@ static inline SkCanvas* CreatePlatformCanvas(int width,
   return CreatePlatformCanvas(width, height, is_opaque, 0, CRASH_ON_FAILURE);
 }
 
-// Takes ownership of the device, so the caller need not call unref().
-SK_API SkCanvas* CreateCanvas(SkDevice* device, OnFailureType failure_type);
+SK_API SkCanvas* CreateCanvas(const skia::RefPtr<SkDevice>& device,
+                              OnFailureType failure_type);
 
 static inline SkCanvas* CreateBitmapCanvas(int width,
                                            int height,