Looks like the D3D9 D32 format isn't available on most GPUs (and doesn't
exist in D3D11) so back GL_DEPTH_COMPONENT32_OES with D24S8 instead to
match D3D11.

BUG=angle:750

Change-Id: I0f7a124544c1c14ba21db20fbf6765d07e244966
Reviewed-on: https://chromium-review.googlesource.com/219080Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>