Simplify TransferMode and Color types.

sky/engine/core/painting/TransferMode.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "sky/engine/config.h"
 #include "sky/engine/core/painting/TransferMode.h"
 
 #include "sky/engine/core/script/dom_dart_state.h"
 #include "sky/engine/tonic/dart_builtin.h"
 #include "sky/engine/tonic/dart_error.h"
 #include "sky/engine/tonic/dart_value.h"
 
 namespace blink {
 
 // Convert dart_mode => SkXfermode::Mode.
-TransferMode DartConverter<TransferMode, void>::FromArgumentsWithNullCheck(
+SkXfermode::Mode DartConverter<TransferMode>::FromArgumentsWithNullCheck(
     Dart_NativeArguments args,
     int index,
     Dart_Handle& exception) {
-  TransferMode result;
+  SkXfermode::Mode result;
 
   Dart_Handle dart_mode = Dart_GetNativeArgument(args, index);
   DCHECK(!LogIfError(dart_mode));
 
   Dart_Handle value =
       Dart_GetField(dart_mode, DOMDartState::Current()->value_handle());
 
   uint64_t mode = 0;
   Dart_Handle rv = Dart_IntegerToUint64(value, &mode);
   DCHECK(!LogIfError(rv));
 
-  result.sk_mode = static_cast<SkXfermode::Mode>(mode);
+  result = static_cast<SkXfermode::Mode>(mode);
   return result;
 }
 
 } // namespace blink