WebGL's getExtension accepts a name that is tested against an ASCII case-insensitive match (http://www.khronos.org/registry/webgl/specs/latest/#5.14.14) Just force lower case for extension names. Patch to follow.
Created attachment 190031 [details] Patch
Comment on attachment 190031 [details] Patch Clearing flags on attachment: 190031 Committed r144427: <http://trac.webkit.org/changeset/144427>
All reviewed patches have been landed. Closing bug.