CanvasRenderingContext2D.getContextAttributes() is not implemented/present in the idl file [1], but is being standarised anyway, see: https://github.com/whatwg/html/issues/2563 and its associated PR https://github.com/whatwg/html/pull/4253. [1] http://git.webkit.org/?p=WebKit.git;a=blob;f=Source/WebCore/html/canvas/CanvasRenderingContext2D.idl
*** This bug has been marked as a duplicate of bug 225173 ***