Confirmed on Linux, 56 and nightly.

Able to reproduce the issue on Windows 10, Ubuntu 14.04 using reported version #56.0.2924.76 and latest canary #58.0.2997.0.

Unable to reproduce this issue on Mac OS as no vertical scrollbar is seen.

Bisect Information:
=====================
Good build: 56.0.2916.0  Revision(431463)

Bad Build : 56.0.2917.0	 Revision(431726)

Change Log URL: 
https://chromium.googlesource.com/chromium/src/+log/266df595a25c40f0ddf6876742149559ff42040b..55444d25b3aec61cbcf053448b3bb999b4bf859b

From the above change log suspecting below change

Review URL: https://codereview.chromium.org/2491953004

bokan@ - Could you please check whether this is caused with respect to your change, if not please help us in assigning it to the right owner.

Thanks...!!

Too late to do anything about this for 56.

Chao, looks like we *should* be applying hover to the box itself. See http://jsfiddle.net/wydsf2vk/81/ note how in Firefox, if you scroll so that the <a> is behind the scrollbar, mousing over it while over the scrollbar should only apply hover to the <div>, not the <a>. In other words, the scrollbars are considered part of the div.

Lets get this fixed for M57. 

Could you please let me by when can I expect chrome 57 to be released officially? And, do you have any workaround for this problem for the time being?

And one more thing is that it is not specific to div. This issue occurs in UL --> li as well, when the list of items is more then the maximum height.

So, in short, it is not working as expected in any of the container where scrollbar appears.

bokan@ I think maybe we should just revert my patch. It can be a scrollbar inside <a> tag: https://jsfiddle.net/xpftxn0e/ 

Re#7: M56 was just promoted to stable so M57 will be stable in about 6 weeks. Unfortunately, I don't think there's a good work around until then, sorry.

Re#8: Revert sounds fine. I don't mean to be specific to <div>. When a scrollbar is required the Element establishes a box. Hovering the scrollbar should apply hover to the Box's Element, but not it's children. 

bokan@ I agree with you. So when we hittest contains a scrollbar, the hittest.element should be the scrollbar's parent.

This issue is also causing flickering scrollbars when 'overflow: auto' is triggered on hover. Try hovering over the scrollbars here: http://jsfiddle.net/stephen61/VTqg5/

Re#11 Confirmed also from my patch.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4d68b33ea8398044d86aa76353e6f7de6880bad6

commit 4d68b33ea8398044d86aa76353e6f7de6880bad6
Author: chaopeng <chaopeng@chromium.org>
Date: Fri Feb 03 21:54:54 2017

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}

[modify] https://crrev.com/4d68b33ea8398044d86aa76353e6f7de6880bad6/third_party/WebKit/Source/core/dom/Document.cpp
[modify] https://crrev.com/4d68b33ea8398044d86aa76353e6f7de6880bad6/third_party/WebKit/Source/web/tests/WebFrameTest.cpp
[add] https://crrev.com/4d68b33ea8398044d86aa76353e6f7de6880bad6/third_party/WebKit/Source/web/tests/data/scrollbar-and-element-hover.html

Verified the Fix on Win 10 and Ubuntu 14.04 using 58.0.3004.0 and its working fine now.
Could you please update issue status to Fixed and merge into M57. 

Deleted: 686678_Feb_6.mp4 442 KB

	686678_Feb_6.mp4 442 KB View Download

Requesting merge to M57

Your change meets the bar and is auto-approved for M57. Please go ahead and merge the CL to branch 2987 manually. Please contact milestone owner if you have questions.
Owners: amineer@(clank), cmasso@(bling), ketakid@(cros), govind@(desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Please merge your change to M57 branch 2987 before 5:00 PM PT, Tuesday (02/07/17) so we can pick it up for next Beta release. Thank you.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/14233c89ca0484b7aa73a7a6d09b7e7155a338b9

commit 14233c89ca0484b7aa73a7a6d09b7e7155a338b9
Author: bokan <bokan@chromium.org>
Date: Tue Feb 07 18:45:19 2017

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}

[modify] https://crrev.com/14233c89ca0484b7aa73a7a6d09b7e7155a338b9/third_party/WebKit/Source/core/dom/Document.cpp
[modify] https://crrev.com/14233c89ca0484b7aa73a7a6d09b7e7155a338b9/third_party/WebKit/Source/web/tests/WebFrameTest.cpp
[add] https://crrev.com/14233c89ca0484b7aa73a7a6d09b7e7155a338b9/third_party/WebKit/Source/web/tests/data/scrollbar-and-element-hover.html

Sorry, I dropped the ball here yesterday and it didn't get merged yesterday. It's in now.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1129f2a8a6a2d6134742e31d5fe2e02bd7946c6b

commit 1129f2a8a6a2d6134742e31d5fe2e02bd7946c6b
Author: bokan <bokan@chromium.org>
Date: Tue Feb 07 21:23:44 2017

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/2687543002 .
Cr-Commit-Position: refs/branch-heads/2987@{#368}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}

[modify] https://crrev.com/1129f2a8a6a2d6134742e31d5fe2e02bd7946c6b/third_party/WebKit/Source/core/dom/Document.cpp
[modify] https://crrev.com/1129f2a8a6a2d6134742e31d5fe2e02bd7946c6b/third_party/WebKit/Source/web/tests/WebFrameTest.cpp

 Issue 695975  has been merged into this issue.