GitLab

This was originally added in 33190c88
for the panels feature, which was then later removed in
566d3644. Currently nothing adds an
observer for this notification.

Bug: 571511
Change-Id: I1ecbcacffd1451d70912895c106858eb616e6a80
Reviewed-on: https://chromium-review.googlesource.com/743857Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512546}