[NTP] Do not use dark mode chips if a background image is set

Do not use dark mode chips (i.e. Most Visited icons, Vasco, fakebox,
etc.) if a background image is applied to the NTP. This includes custom
backgrounds and images from themes.

In order to keep compatibility with M73 versions and Vasco, we use the
negation ":not(.light-chip)" instead of a positive selector such as
".dark-chip".

Bug: 928548
Change-Id: I0284e08485810ce3aad29a288ce4ad21042e7567
Reviewed-on: https://chromium-review.googlesource.com/c/1475207
Reviewed-by: Kyle Milka <kmilka@chromium.org>
Commit-Queue: Kristi Park <kristipark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635847}
4 files changed