IDL: make optional arguments (without default) explicit sometimes

Source/bindings/core/v8/custom/V8CanvasRenderingContext2DCustom.cpp

Index: Source/bindings/core/v8/custom/V8CanvasRenderingContext2DCustom.cpp
diff --git a/Source/bindings/core/v8/custom/V8CanvasRenderingContext2DCustom.cpp b/Source/bindings/core/v8/custom/V8CanvasRenderingContext2DCustom.cpp
index 940ba7c7a75f921a8453249049ac33aec40c712c..dd282198c7352d46ece16e12262f811336731951 100644
--- a/Source/bindings/core/v8/custom/V8CanvasRenderingContext2DCustom.cpp
+++ b/Source/bindings/core/v8/custom/V8CanvasRenderingContext2DCustom.cpp
@@ -78,7 +78,7 @@ void V8CanvasRenderingContext2D::strokeStyleAttributeSetterCustom(v8::Local<v8::
         impl->setStrokeStyle(canvasStyle);
     } else {
         TOSTRING_VOID(V8StringResource<>, colorString, value);
-        impl->setStrokeColor(colorString);
+        impl->setStrokeColor(colorString, makeOptionalMissing<float>());
     }
 }
 
@@ -95,7 +95,7 @@ void V8CanvasRenderingContext2D::fillStyleAttributeSetterCustom(v8::Local<v8::Va
         impl->setFillStyle(canvasStyle);
     } else {
         TOSTRING_VOID(V8StringResource<>, colorString, value);
-        impl->setFillColor(colorString);
+        impl->setFillColor(colorString, makeOptionalMissing<float>());
     }
 }