IDL: make optional arguments (without default) explicit sometimes

Source/core/html/canvas/CanvasPathMethods.idl

Index: Source/core/html/canvas/CanvasPathMethods.idl
diff --git a/Source/core/html/canvas/CanvasPathMethods.idl b/Source/core/html/canvas/CanvasPathMethods.idl
index 2c37810cef724edd0688127b90dfab4ad2bec9b6..7448899d834630e008898feb3596543b781cd1fa 100644
--- a/Source/core/html/canvas/CanvasPathMethods.idl
+++ b/Source/core/html/canvas/CanvasPathMethods.idl
@@ -15,6 +15,6 @@
     void bezierCurveTo(unrestricted float cp1x, unrestricted float cp1y, unrestricted float cp2x, unrestricted float cp2y, unrestricted float x, unrestricted float y);
     [RaisesException] void arcTo(unrestricted float x1, unrestricted float y1, unrestricted float x2, unrestricted float y2, unrestricted float radius);
     void rect(unrestricted float x, unrestricted float y, unrestricted float width, unrestricted float height);
-    [RaisesException] void arc(unrestricted float x, unrestricted float y, unrestricted float radius, unrestricted float startAngle, unrestricted float endAngle, [Default=Undefined] optional boolean anticlockwise);
-    [RaisesException] void ellipse(unrestricted float x, unrestricted float y, unrestricted float radiusX, unrestricted float radiusY, unrestricted float rotation, unrestricted float startAngle, unrestricted float endAngle, [Default=Undefined] optional boolean anticlockwise);
+    [RaisesException] void arc(unrestricted float x, unrestricted float y, unrestricted float radius, unrestricted float startAngle, unrestricted float endAngle, optional boolean anticlockwise);
+    [RaisesException] void ellipse(unrestricted float x, unrestricted float y, unrestricted float radiusX, unrestricted float radiusY, unrestricted float rotation, unrestricted float startAngle, unrestricted float endAngle, optional boolean anticlockwise);
 };