GitLab

This CL:
- Introduces generation of R.color.background_color from the JSON
  config via mustache
- Renames manifest_mustache_pass to mustache_pass

BUG=969591

Change-Id: Ic434dc69673dfab19559c59894a3686db58b4e09
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1644752
Commit-Queue: Peter Kotwicz <pkotwicz@chromium.org>
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#666597}