[Mac] Fix for fullscreen toolbar

[Mac] Fix for fullscreen toolbar

Added back mouse tracking to fix an edge case where the menu
bar disappears when but the mouse is still hovering the toolbar.

The tracking area is only used to keep the toolbar active when this
happens. The toolbar will hide when the mouse leaves the tracking
area.

BUG=639562
Review-Url: https://codereview.chromium.org/2272783002
Cr-Commit-Position: refs/heads/master@{#414888}
(cherry picked from commit e776f9c0602bafaf7ec33d022f543e86c4191a8f)

Committed: https://chromium.googlesource.com/chromium/src/+/f47d14d961ef70dea76db3e01527783158a2f36a

[spqchan, 2016-08-29 17:11:48]

Description was changed from

==========
[Mac] Fix for fullscreen toolbar

Added back mouse tracking to fix an edge case where the menu
bar disappears when but the mouse is still hovering the toolbar.

The tracking area is only used to keep the toolbar active when this
happens. The toolbar will hide when the mouse leaves the tracking
area.

BUG=639562

Review-Url: https://codereview.chromium.org/2272783002
Cr-Commit-Position: refs/heads/master@{#414888}
(cherry picked from commit e776f9c0602bafaf7ec33d022f543e86c4191a8f)
==========

to

==========
[Mac] Fix for fullscreen toolbar

Added back mouse tracking to fix an edge case where the menu
bar disappears when but the mouse is still hovering the toolbar.

The tracking area is only used to keep the toolbar active when this
happens. The toolbar will hide when the mouse leaves the tracking
area.

BUG=639562

Review-Url: https://codereview.chromium.org/2272783002
Cr-Commit-Position: refs/heads/master@{#414888}
(cherry picked from commit e776f9c0602bafaf7ec33d022f543e86c4191a8f)

Committed:
https://chromium.googlesource.com/chromium/src/+/f47d14d961ef70dea76db3e01527...
==========

[spqchan, 2016-08-29 17:11:50]

Committed patchset #1 (id:1) manually as
f47d14d961ef70dea76db3e01527783158a2f36a.