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]
Comment on attachment 190031 [details]
Clearing flags on attachment: 190031
Committed r144427: <http://trac.webkit.org/changeset/144427>
All reviewed patches have been landed. Closing bug.