Update the button visibility when mouse enters or exits from notification surface window

Update the button visibility when mouse enters or exits from notification surface window

The outer view's ONMOUSEENTERED/EXITED are not called on toast, so we need to handle the window's event handlers.

BUG=728915
TEST=manual (issue is not happened)

Review-Url: https://codereview.chromium.org/2922643002
Cr-Commit-Position: refs/heads/master@{#477927}
(cherry picked from commit 7b1b44becb55f7920992b9027307531932f83ce7)

Review-Url: https://codereview.chromium.org/2939673002 .
Cr-Commit-Position: refs/branch-heads/3112@{#314}
Cr-Branched-From: b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}
Committed: https://chromium.googlesource.com/chromium/src/+/ee53fcd185bc5a713a76bda3d8836328e4952426

[yoshiki, 2017-06-13 04:37:37]

Description was changed from

==========
Update the button visibility when mouse enters or exits from notification
surface window

The outer view's ONMOUSEENTERED/EXITED are not called on toast, so we need to
handle the window's event handlers.

BUG=728915
TEST=manual (issue is not happened)

Review-Url: https://codereview.chromium.org/2922643002
Cr-Commit-Position: refs/heads/master@{#477927}
(cherry picked from commit 7b1b44becb55f7920992b9027307531932f83ce7)
==========

to

==========
Update the button visibility when mouse enters or exits from notification
surface window

The outer view's ONMOUSEENTERED/EXITED are not called on toast, so we need to
handle the window's event handlers.

BUG=728915
TEST=manual (issue is not happened)

Review-Url: https://codereview.chromium.org/2922643002
Cr-Commit-Position: refs/heads/master@{#477927}
(cherry picked from commit 7b1b44becb55f7920992b9027307531932f83ce7)

Review-Url: https://codereview.chromium.org/2939673002 .
Cr-Commit-Position: refs/branch-heads/3112@{#314}
Cr-Branched-From:
b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}
Committed:
https://chromium.googlesource.com/chromium/src/+/ee53fcd185bc5a713a76bda3d883...
==========

[yoshiki, 2017-06-13 04:37:39]

Committed patchset #1 (id:1) manually as
ee53fcd185bc5a713a76bda3d8836328e4952426.