Add support for new canvas ellipse method.

Source/core/html/canvas/CanvasRenderingContext2D.idl

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 106 matching lines @@
     void rect([Default=Undefined] optional float x,
               [Default=Undefined] optional float y,
               [Default=Undefined] optional float width,
               [Default=Undefined] optional float height);
     [RaisesException] void arc([Default=Undefined] optional float x,
              [Default=Undefined] optional float y,
              [Default=Undefined] optional float radius,
              [Default=Undefined] optional float startAngle,
              [Default=Undefined] optional float endAngle,
              [Default=Undefined] optional boolean anticlockwise);
+    [RaisesException] void ellipse([Default=Undefined] optional float x,

[Stephen Chennney, 2013/04/26 14:51:03]

What good is an optional default=undefined value? From the code it seems that
you must define all of the parameters in order to draw anything.

[dshwang, 2013/04/26 15:23:33]

Aha, I see. I'll put [Default=Undefined] carefully after reading spec again.

BTW, I'll file another bug to remove [Default=Undefined] from other API (e.g.
arc()). I followed arc() without thought.

+            [Default=Undefined] optional float y,
+            [Default=Undefined] optional float radiusX,
+            [Default=Undefined] optional float radiusY,
+            [Default=Undefined] optional float rotation,
+            [Default=Undefined] optional float startAngle,
+            [Default=Undefined] optional float endAngle,
+            [Default=Undefined] optional boolean anticlockwise);
 
     void fill(optional CanvasWindingRule winding);
     void stroke();
     void clip(optional CanvasWindingRule winding);
     boolean isPointInPath([Default=Undefined] optional float x,
                           [Default=Undefined] optional float y,
                           optional CanvasWindingRule winding);
     boolean isPointInStroke([Default=Undefined] optional float x,
                             [Default=Undefined] optional float y);
 
@@ skipping 74 matching lines @@
                            [Default=Undefined] optional float sw, [Default=Undefined] optional float sh);
 
     [RaisesException] ImageData webkitGetImageDataHD([Default=Undefined] optional float sx, [Default=Undefined] optional float sy,
                                    [Default=Undefined] optional float sw, [Default=Undefined] optional float sh);
 
     readonly attribute float webkitBackingStorePixelRatio;
 
     attribute boolean webkitImageSmoothingEnabled;
 };