Simplify TransferMode and Color types.

sky/engine/core/painting/ColorFilter.h

Index: sky/engine/core/painting/ColorFilter.h
diff --git a/sky/engine/core/painting/ColorFilter.h b/sky/engine/core/painting/ColorFilter.h
index 5b879ee027eb13af7b8b6c28c5db772663657313..eab966388efa777acee7122c4ac0f5067fd702de 100644
--- a/sky/engine/core/painting/ColorFilter.h
+++ b/sky/engine/core/painting/ColorFilter.h
@@ -18,8 +18,8 @@ class ColorFilter : public RefCounted<ColorFilter>, public DartWrappable {
   DEFINE_WRAPPERTYPEINFO();
  public:
   ~ColorFilter() override;
-  static PassRefPtr<ColorFilter> create(CanvasColor color,
-                                        TransferMode transfer_mode);
+  static PassRefPtr<ColorFilter> create(SkColor color,
+                                        SkXfermode::Mode transfer_mode);
 
   SkColorFilter* filter() { return filter_.get(); }