CSSOM: Support CSS.q() factory function

We add tests for a number of factory functions.

The case for q() Hz() kHz() follows the current spec.
https://github.com/w3c/css-houdini-drafts/issues/504

BUG=421907,545318

Change-Id: I20e05a26738b8a8dd46d683e9f6d4730e5f4f607
Reviewed-on: https://chromium-review.googlesource.com/750403
Commit-Queue: Eric Willigers <ericwilligers@chromium.org>
Reviewed-by: Darren Shen <shend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#514061}
6 files changed