Adding supported checks for WebGL

tools/dom/idl/dart/dart.idl

Index: tools/dom/idl/dart/dart.idl
diff --git a/tools/dom/idl/dart/dart.idl b/tools/dom/idl/dart/dart.idl
index e823e52c97ce77b47b08667f3229361c029f011b..032795fb36fef371d260d8e89b783fa4277761a9 100644
--- a/tools/dom/idl/dart/dart.idl
+++ b/tools/dom/idl/dart/dart.idl
@@ -44,6 +44,9 @@ interface Console {
 interface HTMLCanvasElement {
   [Suppressed] DOMString toDataURL([TreatNullAs=NullString, TreatUndefinedAs=NullString,Optional=DefaultIsUndefined] in DOMString type) raises(DOMException);
   [Custom] DOMString toDataURL([TreatNullAs=NullString, TreatUndefinedAs=NullString,Optional=DefaultIsUndefined] in DOMString type, [Optional] in float quality) raises(DOMException);
+
+  [Suppressed] DOMObject getContext([Optional=DefaultIsUndefined] in DOMString contextId);
+  [Custom] CanvasRenderingContext getContext([Optional=DefaultIsUndefined] in DOMString contextId, [Optional] in Dictionary attrs);

[sra1, 2013/01/29 02:17:34]

Drop the [Optional=DefaultIsUndefined]
The generator ignores that since in JS it forces passing missing arguments -
something required to not break existing code that is missing mandatory
arguments.

[blois, 2013/01/29 21:50:08]

Done.

 };
 
 [Supplemental]