Retire the old TVariableInfoList structure, and use the new
objects which we will expose more directly through the API.

BUG=angle:466

Change-Id: I999a97369bfb67cf73cd659c4fe885b41429d304
Reviewed-on: https://chromium-review.googlesource.com/205839Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Nicolas Capens <capn@chromium.org>