Change call-sites now that SkCanvas is not ref-counted

ppapi/proxy/ppb_image_data_proxy.cc

Index: ppapi/proxy/ppb_image_data_proxy.cc
diff --git a/ppapi/proxy/ppb_image_data_proxy.cc b/ppapi/proxy/ppb_image_data_proxy.cc
index bde81b43fb62c550ca95f29970a585b655871373..b4415fdada0f5c3cac0b14d47ca9bdf82cb9bd4c 100644
--- a/ppapi/proxy/ppb_image_data_proxy.cc
+++ b/ppapi/proxy/ppb_image_data_proxy.cc
@@ -391,10 +391,8 @@ void* PlatformImageData::Map() {
       return NULL;
 
     const bool is_opaque = false;
-    mapped_canvas_ =
-        sk_sp<SkCanvas>(transport_dib_->GetPlatformCanvas(desc_.size.width,
-                                                          desc_.size.height,
-                                                          is_opaque));
+    mapped_canvas_ = transport_dib_->GetPlatformCanvas(
+        desc_.size.width, desc_.size.height, is_opaque);
     if (!mapped_canvas_.get())
       return NULL;
   }