Change hover element to scrollbar's parent when hit test contains scrollbar

Change hover element to scrollbar's parent when hit test contains scrollbar

This issue is caused by remove hit test element in
|Document::updateHoverActiveState| when hit test contains scrollbar. Instead we
should replace the hit test element to be scrollbar's parent when hitting a
scrollbar.

BUG=686678
Review-Url: https://codereview.chromium.org/2668133003
Cr-Commit-Position: refs/heads/master@{#448078}
(cherry picked from commit 4d68b33ea8398044d86aa76353e6f7de6880bad6)

Review-Url: https://codereview.chromium.org/2679233002 .
Cr-Commit-Position: refs/branch-heads/2987@{#363}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed: https://chromium.googlesource.com/chromium/src/+/14233c89ca0484b7aa73a7a6d09b7e7155a338b9

[bokan, 2017-02-07 18:47:02]

Description was changed from

==========
Change hover element to scrollbar's parent when hit test contains scrollbar

This issue is caused by remove hit test element in
|Document::updateHoverActiveState| when hit test contains scrollbar. Instead we
should replace the hit test element to be scrollbar's parent when hitting a
scrollbar.

BUG=686678

Review-Url: https://codereview.chromium.org/2668133003
Cr-Commit-Position: refs/heads/master@{#448078}
(cherry picked from commit 4d68b33ea8398044d86aa76353e6f7de6880bad6)
==========

to

==========
Change hover element to scrollbar's parent when hit test contains scrollbar

This issue is caused by remove hit test element in
|Document::updateHoverActiveState| when hit test contains scrollbar. Instead we
should replace the hit test element to be scrollbar's parent when hitting a
scrollbar.

BUG=686678

Review-Url: https://codereview.chromium.org/2668133003
Cr-Commit-Position: refs/heads/master@{#448078}
(cherry picked from commit 4d68b33ea8398044d86aa76353e6f7de6880bad6)

Review-Url: https://codereview.chromium.org/2679233002 .
Cr-Commit-Position: refs/branch-heads/2987@{#363}
Cr-Branched-From:
ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed:
https://chromium.googlesource.com/chromium/src/+/14233c89ca0484b7aa73a7a6d09b...
==========

[bokan, 2017-02-07 18:47:03]

Committed patchset #1 (id:1) manually as
14233c89ca0484b7aa73a7a6d09b7e7155a338b9.