Enable skipped webgl conformance tests on mac gpu ati bots.

First step, mark them as Fail (instead of Skip) just to be safe.

Tested with 10.8 on one mac with ati gpu, all webgl conformance 1.0.2 are passing.

BUG=308328
TEST=mac gpu ati bots
TBR=kbr@chromium.org

Review URL: https://codereview.chromium.org/175453003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252600 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252600