Sky: Add a DartConverterEnum and use that for all our enum needs.

sky/engine/core/painting/CanvasGradient.h

 // 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.
 
 #ifndef SKY_ENGINE_CORE_PAINTING_CANVASGRADIENT_H_
 #define SKY_ENGINE_CORE_PAINTING_CANVASGRADIENT_H_
 
 #include "sky/engine/core/painting/CanvasColor.h"
 #include "sky/engine/core/painting/Point.h"
 #include "sky/engine/core/painting/Shader.h"
 #include "sky/engine/tonic/dart_wrappable.h"
 #include "third_party/skia/include/effects/SkGradientShader.h"
 
 namespace blink {
 
+class TileMode {};
+
+template <>
+struct DartConverter<TileMode> : public DartConverterEnum<SkShader::TileMode> {};
+
+COMPILE_ASSERT(SkShader::kTileModeCount == 3, Need_to_update_Gradient_dart);
+
 class CanvasGradient : public Shader {
     DEFINE_WRAPPERTYPEINFO();
  public:
   ~CanvasGradient() override;
   static PassRefPtr<CanvasGradient> create();
 
   void initLinear(const Vector<Point>& end_points,
                   const Vector<SkColor>& colors,
                   const Vector<float>& color_stops,
-                  unsigned tile_mode);
+                  SkShader::TileMode tile_mode);
   void initRadial(const Point& center,
                   double radius,
                   const Vector<SkColor>& colors,
                   const Vector<float>& color_stops,
-                  unsigned tile_mode);
+                  SkShader::TileMode tile_mode);
 
  private:
   CanvasGradient();
 };
 
 } // namespace blink
 
 #endif  // SKY_ENGINE_CORE_PAINTING_CANVASGRADIENT_H_