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

sky/engine/core/painting/CanvasGradient.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/CanvasGradient.h"
 
 namespace blink {
 
 PassRefPtr<CanvasGradient> CanvasGradient::create() {
   return adoptRef(new CanvasGradient());
 }
 
 void CanvasGradient::initLinear(const Vector<Point>& end_points,
                                 const Vector<SkColor>& colors,
                                 const Vector<float>& color_stops,
-                                unsigned tile_mode) {
+                                SkShader::TileMode tile_mode) {
   ASSERT(end_points.size() == 2);
   ASSERT(colors.size() == color_stops.size() || color_stops.data() == nullptr);
   ASSERT(tile_mode < SkShader::kTileModeCount);
   SkPoint sk_end_points[2];
   for (int i = 0; i < 2; ++i)
     sk_end_points[i] = end_points[i].sk_point;
 
   // TODO(mpcomplete): allow setting the TileMode.
   SkShader* shader = SkGradientShader::CreateLinear(
       sk_end_points, colors.data(), color_stops.data(), colors.size(),
-      static_cast<SkShader::TileMode>(tile_mode));
+      tile_mode);
   set_shader(adoptRef(shader));
 }
 
 void CanvasGradient::initRadial(const Point& center,
                                 double radius,
                                 const Vector<SkColor>& colors,
                                 const Vector<float>& color_stops,
-                                unsigned tile_mode) {
+                                SkShader::TileMode tile_mode) {
   ASSERT(colors.size() == color_stops.size() || color_stops.data() == nullptr);
   ASSERT(tile_mode < SkShader::kTileModeCount);
 
   SkShader* shader = SkGradientShader::CreateRadial(
       center.sk_point, radius, colors.data(), color_stops.data(), colors.size(),
-      static_cast<SkShader::TileMode>(tile_mode));
+      tile_mode);
   set_shader(adoptRef(shader));
 }
 
 CanvasGradient::CanvasGradient()
     : Shader(nullptr)
 {
 }
 
 CanvasGradient::~CanvasGradient()
 {
 }
 
 }  // namespace blink