We were using the input stride from the disabled vertex attribute.
This was breaking the gl-disabled-vertex-attrib test in D3D9.

BUG=angle:550

Change-Id: Ia5a37dc39105fe8ec92f4adbee3cfb2905e82676
Reviewed-on: https://chromium-review.googlesource.com/191932Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>