Implement GL_CHROMIUM_sync_query for GL. BUG=angleproject:1366 Change-Id: I9e44679754eb704b390191c28206dedc3dc7cc4f Reviewed-on: https://chromium-review.googlesource.com/367082 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org>