This approach consolidates our two methods, and lets us reuse the
same code for both methods of variable collection.

BUG=angle:466

Change-Id: Ie92f76ff0b6d0d0dbfd211a234d0ab86290fa798
Reviewed-on: https://chromium-review.googlesource.com/213504Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Nicolas Capens <capn@chromium.org>