Add GL_OES_EGL_image functions. Needed to work on Chrome OS. BUG=angleproject:1297 Change-Id: I78e18472780745f73257c8954f263d236ff92180 Reviewed-on: https://chromium-review.googlesource.com/323470 Tryjob-Request: Frank Henigman <fjhenigman@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Frank Henigman <fjhenigman@chromium.org>