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

skia/ext/bitmap_platform_device_mac.cc

Index: skia/ext/bitmap_platform_device_mac.cc
diff --git a/skia/ext/bitmap_platform_device_mac.cc b/skia/ext/bitmap_platform_device_mac.cc
index c97e6fbdd42b010dc80abb6d8d44b7f84be90d8b..543d62a2ee469dc0ba40a2b6feb464a6bf76e4cd 100644
--- a/skia/ext/bitmap_platform_device_mac.cc
+++ b/skia/ext/bitmap_platform_device_mac.cc
@@ -202,7 +202,6 @@ BitmapPlatformDevice::BitmapPlatformDevice(
 }
 
 BitmapPlatformDevice::~BitmapPlatformDevice() {
-  data_->unref();
 }
 
 CGContextRef BitmapPlatformDevice::GetBitmapContext() {
@@ -265,14 +264,15 @@ SkDevice* BitmapPlatformDevice::onCreateCompatibleDevice(
 
 SkCanvas* CreatePlatformCanvas(CGContextRef ctx, int width, int height,
                                bool is_opaque, OnFailureType failureType) {
-  SkDevice* dev = BitmapPlatformDevice::Create(ctx, width, height, is_opaque);
+  skia::RefPtr<SkDevice> dev =
+      BitmapPlatformDevice::Create(ctx, width, height, is_opaque);
   return CreateCanvas(dev, failureType);
 }
 
 SkCanvas* CreatePlatformCanvas(int width, int height, bool is_opaque,
                                uint8_t* data, OnFailureType failureType) {
-  SkDevice* dev = BitmapPlatformDevice::CreateWithData(data, width, height,
-                                                       is_opaque);
+  skia::RefPtr<SkDevice> dev =
+      BitmapPlatformDevice::CreateWithData(data, width, height, is_opaque);
   return CreateCanvas(dev, failureType);
 }