EGL: Implement EGL Image extensions. BUG=angleproject:2507 Change-Id: Ica33166e9e23e933977c3ab034d4f5a8cada9fb1 Reviewed-on: https://chromium-review.googlesource.com/1143454 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>