GitLab

In Chrome OS, when the adaptive icon feature is enabled, add the white
background and mask to the web app maskable icon.

BUG=1083331

Change-Id: Ibf5e87cdd489a470c8ce4d4c5c54f74290652c3b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2359316Reviewed-by: Dominick Ng <dominickn@chromium.org>
Commit-Queue: Nancy Wang <nancylingwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798568}