Disable EXT_depth_textures on AMD D3D9 devices. BUG=angle:839 Change-Id: Ia8c24db98a31141994e22b25efbdfddaa4eced49 Reviewed-on: https://chromium-review.googlesource.com/231996 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Kenneth Russell <kbr@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>