Fix wrong type for GL_STENCIL_INDEX8. This was stored as DEPTH_STENCIL when it should be STENCIL. BUG=angleproject:1228 Change-Id: I34c226a273cf962e83a040630bedbefa0f9ee382 Reviewed-on: https://chromium-review.googlesource.com/362623 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>