V8 Binding: Introduce toNativeWithTypeCheck

Source/bindings/v8/custom/V8CanvasRenderingContext2DCustom.cpp

Index: Source/bindings/v8/custom/V8CanvasRenderingContext2DCustom.cpp
diff --git a/Source/bindings/v8/custom/V8CanvasRenderingContext2DCustom.cpp b/Source/bindings/v8/custom/V8CanvasRenderingContext2DCustom.cpp
index 3ceda56208baf8c3a527c78b9dff921efacb8a60..0351c804e0e38a038d51031b5a277d4a0d1a5185 100644
--- a/Source/bindings/v8/custom/V8CanvasRenderingContext2DCustom.cpp
+++ b/Source/bindings/v8/custom/V8CanvasRenderingContext2DCustom.cpp
@@ -59,13 +59,10 @@ static v8::Handle<v8::Value> toV8Object(CanvasStyle* style, v8::Handle<v8::Objec
 
 static PassRefPtr<CanvasStyle> toCanvasStyle(v8::Handle<v8::Value> value, v8::Isolate* isolate)
 {
-    if (V8CanvasGradient::hasInstance(value, isolate))
-        return CanvasStyle::createFromGradient(V8CanvasGradient::toNative(v8::Handle<v8::Object>::Cast(value)));
-
-    if (V8CanvasPattern::hasInstance(value, isolate))
-        return CanvasStyle::createFromPattern(V8CanvasPattern::toNative(v8::Handle<v8::Object>::Cast(value)));
-
-    return 0;
+    RefPtr<CanvasStyle> canvasStyle = CanvasStyle::createFromGradient(V8CanvasGradient::toNativeWithTypeCheck(isolate, value));
+    if (canvasStyle)
+        return canvasStyle;
+    return CanvasStyle::createFromPattern(V8CanvasPattern::toNativeWithTypeCheck(isolate, value));
 }
 
 void V8CanvasRenderingContext2D::strokeStyleAttributeGetterCustom(const v8::PropertyCallbackInfo<v8::Value>& info)