mash: QuickLaunch shelf item doesn't respond to selection.
(1) Run "chrome --mash" on ToT (should see a chrome window in front)
(2) Click the "QuickLaunch" shelf item with the default/page icon [repeatedly].
Expected: The QuickLaunch window is brought to the front, [minimized, restored, repeat].
Actual: Nothing happens, debugging shows the shelf item delegate isn't notified...

I'm not sure why the QuickLaunch shelf item delegate is no longer notified.
Other ShelfWindowWatcherItemDelegate instances (task manager, cros settings) work fine.

Found while working on my context menu CL; QuickLaunch's context menu will also break:
  https://chromium-review.googlesource.com/c/571517