Add support for new canvas ellipse method.

Source/core/html/canvas/CanvasRenderingContext2D.idl

Index: Source/core/html/canvas/CanvasRenderingContext2D.idl
diff --git a/Source/core/html/canvas/CanvasRenderingContext2D.idl b/Source/core/html/canvas/CanvasRenderingContext2D.idl
index ec98b03747821a8aa617a5097ad8679632fe23d7..275cab9a949725ea7a9b6593428c268fb36e4f56 100644
--- a/Source/core/html/canvas/CanvasRenderingContext2D.idl
+++ b/Source/core/html/canvas/CanvasRenderingContext2D.idl
@@ -124,6 +124,14 @@ interface CanvasRenderingContext2D : CanvasRenderingContext {
              [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();