Chrome Version: 52.0.2743.10 (Official Build) 18f7321a2c4403368e9e5e53f5396ede2d60b2f7-refs/branch-heads/2743@{#70}
OS: Mac (10.10.5, 10.11.5)

Steps:
1. Launch chrome,navigate to http://plugindoc.mozdev.org/testpages/pdf.html
2. Hover mouse on embedded pdf and scroll down via mouse wheel and observe.

Actual: Scroll bar bounces back after scrolling embedded pdf via mouse wheel.

Expected: Scroll bar should work smoothly after scrolling embedded pdf via mouse wheel.

This is a regression issue broken in 'M51' and below is bisect info.

Good Build: 51.0.2686.0
Bad Build:  51.0.2687.0

Narrow bisect:
https://chromium.googlesource.com/chromium/src/+log/6bebadddb399ad1c1f91592efed410040617e708..5840ac85a7c912d9ddb764007b6a9ec65a26ad22?pretty=fuller&n=30

Suspecting: r382345 ?

Kindly help to re-assign, if your changes are not cause for this issue.

Note: Issue not seen on Win & Linux OS.
 

Deleted: Actual_Video.mov 1.8 MB

Actual_Video.mov 1.8 MB Download

Deleted: Expected_Video.mov 618 KB

Expected_Video.mov 618 KB Download