Fix GL_MAX_SAMPLES query for ES3 when the extension is missing. This query was added in both ES3 and ANGLE_framebuffer_multisample but the code was never updated to accept it for an ES3 context without the extension present. Caught by the angle passthrough command decoder fuzzer. BUG=602737 Change-Id: Ic9a8c67747777ef48e1dd227110482998fee75ce Reviewed-on: https://chromium-review.googlesource.com/440651 Reviewed-by: Corentin Wallez <cwallez@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>