Implement eglQueryContext BUG=angle:895 Change-Id: I5e709f772d6222cdb7b5d7c060830a75eac9f815 Reviewed-on: https://chromium-review.googlesource.com/246490 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org>