Since these types originate from the translator, use an appropriate
namespace. Also rename some of the gl helper functions to be more
specific to their functionality.

BUG=angle:466

Change-Id: Idc29987b2053b3c40748dd46b581f3dbd8a6fd61
Reviewed-on: https://chromium-review.googlesource.com/204680Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>