views: random cleanup from removing support for mus

This functionality was added purely for mus and is no longer necessary.

BUG=958241
TEST=purely dead code removal

Change-Id: I856576f9adef9728d837d56e82f94a87aeea040b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1610497
Commit-Queue: Scott Violet <sky@chromium.org>
Reviewed-by: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659207}
7 files changed