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

skia/ext/vector_platform_device_skia.cc

Index: skia/ext/vector_platform_device_skia.cc
diff --git a/skia/ext/vector_platform_device_skia.cc b/skia/ext/vector_platform_device_skia.cc
index 14376222b49c4dd397acf76b85e052db94e613f6..d8d3084afcbe40fadf20f19ee08a75184b032ef6 100644
--- a/skia/ext/vector_platform_device_skia.cc
+++ b/skia/ext/vector_platform_device_skia.cc
@@ -41,9 +41,8 @@ PlatformSurface VectorPlatformDeviceSkia::BeginPlatformPaint() {
   // and return the context from it, then layer on the raster data as an
   // image in EndPlatformPaint.
   DCHECK(raster_surface_ == NULL);
-  raster_surface_ = BitmapPlatformDevice::CreateAndClear(width(), height(),
-                                                         false);
-  raster_surface_->unref();  // SkRefPtr and create both took a reference.
+  raster_surface_ = skia::AdoptRef(
+      BitmapPlatformDevice::CreateAndClear(width(), height(), false));
   return raster_surface_->BeginPlatformPaint();
 }
 
@@ -58,7 +57,7 @@ void VectorPlatformDeviceSkia::EndPlatformPaint() {
   drawSprite(draw, raster_surface_->accessBitmap(false), 0, 0, paint);
   // BitmapPlatformDevice matches begin and end calls.
   raster_surface_->EndPlatformPaint();
-  raster_surface_ = NULL;
+  raster_surface_.clear();
 }
 
 #if defined(OS_WIN)