Update the draw calls to return Error objects. BUG=angle:520 Change-Id: I3330ba2dbe095fc9460789822a938420a80a149f Reviewed-on: https://chromium-review.googlesource.com/213823 Reviewed-by: Jamie Madill <jmadill@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>