Use IDL union types for CanvasRenderingContext2D.{fill,stroke}Style

Source/core/html/canvas/CanvasRenderingContext2D.h

Index: Source/core/html/canvas/CanvasRenderingContext2D.h
diff --git a/Source/core/html/canvas/CanvasRenderingContext2D.h b/Source/core/html/canvas/CanvasRenderingContext2D.h
index 05fe12f4380a0956f1e886ee7a7b8928c1eedce1..988591d85fecff0c68312ffdc0c733e362f4257f 100644
--- a/Source/core/html/canvas/CanvasRenderingContext2D.h
+++ b/Source/core/html/canvas/CanvasRenderingContext2D.h
@@ -79,11 +79,11 @@ public:
     }
     virtual ~CanvasRenderingContext2D();
 
-    CanvasStyle* strokeStyle() const;
-    void setStrokeStyle(PassRefPtrWillBeRawPtr<CanvasStyle>);
+    void strokeStyle(StringOrCanvasGradientOrCanvasPattern&) const;
+    void setStrokeStyle(const StringOrCanvasGradientOrCanvasPattern&);
 
-    CanvasStyle* fillStyle() const;
-    void setFillStyle(PassRefPtrWillBeRawPtr<CanvasStyle>);
+    void fillStyle(StringOrCanvasGradientOrCanvasPattern&) const;
+    void setFillStyle(const StringOrCanvasGradientOrCanvasPattern&);
 
     float lineWidth() const;
     void setLineWidth(float);