In the component type lexicon, we only use float/int/uint/norm,
and we were marking the D3D9 short vertex attributes as short.

This fixes the WebGL Test gl-vertexattribpointer-offsets.

BUG=angle:550

Change-Id: I3853df8bad5c98b8d0986bfa4ea73d254264ad56
Reviewed-on: https://chromium-review.googlesource.com/191950Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>