Simplify TransferMode and Color types.

sky/engine/core/painting/TransferMode.h

Index: sky/engine/core/painting/TransferMode.h
diff --git a/sky/engine/core/painting/TransferMode.h b/sky/engine/core/painting/TransferMode.h
index 6916bdac7623aa49de5d72672e909b11ff08228c..6033f4d250be888d0ca1dac6b235de34b6d6c90d 100644
--- a/sky/engine/core/painting/TransferMode.h
+++ b/sky/engine/core/painting/TransferMode.h
@@ -13,16 +13,13 @@
 
 namespace blink {
 
-class TransferMode {
- public:
-  SkXfermode::Mode sk_mode;
-};
+class TransferMode {};
 
-template<>
-struct DartConverter<TransferMode, void> {
-  static TransferMode FromArgumentsWithNullCheck(Dart_NativeArguments args,
-                                                 int index,
-                                                 Dart_Handle& exception);
+template <>
+struct DartConverter<TransferMode> {
+  static SkXfermode::Mode FromArgumentsWithNullCheck(Dart_NativeArguments args,
+                                                     int index,
+                                                     Dart_Handle& exception);
 };
 
 } // namespace blink