Fix checks for GL_ETC1_RGB8_OES, disable it on D3D11. The GL backend was checking the wrong extension for GL_ETC1_RGB8_OES. WebGL doesn't want to expose compressed formats that are emulated, disable this format in D3D11 where it is always emulated. BUG=98314 Change-Id: I1ba8418ad1578c070891828b87e49cf894dabc29 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1700574 Reviewed-by: Jonah Ryan-Davis <jonahr@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>