GitLab

- Move menu bar locking into ScopedMenuBarLock to get a stronger
  guarantee that the menu bar is left unlocked on exiting fullscreen.

- Use a different test for whether there should be a tracking area.

- Lock and unlock the menu bar from -[FullscreenToolbarMouseTracker
  mouseEntered:] and -mouseExited: directly. Also don't remove the
  tracking area in mouseExited:, this caused a case where the tracking
  area got removed while the menu bar was still visible.

- Remove a couple of unit tests which mostly repeated existing tests but
  also tested assumptions that are no longer valid. It might be good to
  add an interactive UI test in the future, or a unit test for
  FullscreenToolbarMouseTracker.

Background
----------

The menu bar and toolbar would get stuck if you enter fullscreen and
either:

1. Move the mouse to the top of the screen, then move it down over the
   toolbar, then back up to the top of the screen, then down to the
   middle of the screen. Cause: the tracking was incorrectly removed in
   mouseExited:.

2. Move the mouse to the top of the screen, then open a menu, move the
   mouse down to the middle of the screen, and click to close the menu.
   Cause: The menu bar overlaps the window when it drops down. Moving
   the mouse over the menu bar fired mouseExited:, but the old code used
   -mouseInsideTrackingArea, which still returned YES because the mouse
   was technically inside the tracking area even though mouseExited: had
   already fired and wouldn't fire again.

Bug: 762160
Change-Id: Ia15228be8d62e16a66a712f78bd1c8fe62dbef26
Reviewed-on: https://chromium-review.googlesource.com/688414Reviewed-by: Robert Sesek <rsesek@chromium.org>
Reviewed-by: Sarah Chan <spqchan@chromium.org>
Commit-Queue: Sidney San Martín <sdy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505168}