Navi: Replace active indicator mixin with CSS variable

Bug: 973674
Change-Id: I88399b1b8a9b3cf82caa08ea11c0525294edcd7f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1674454
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Commit-Queue: John Lee <johntlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672202}
2 files changed