Make TexImage2D(ImageBitmap) supports some more formats

With crbug.com/626431 fixed, texImage2D(ImageBitmap) is able to support
more formats for WebGL2.

BUG=
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.win:win_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2165243002
Cr-Commit-Position: refs/heads/master@{#406858}
1 file changed