Chrome Version: 55.0.2861.0 (Official Build) 9cedf75377d817c6b32a01f1d30fbe10663b8bb8-refs/heads/master@{#418732}- 32/64 bit.
OS: Windows (7,8,8.1,10), Linux (14.04 LTS), Mac OS X(10.10.5, 10.11.4)

Steps: 
1. Launch Chrome and navigate chrome://policy
2. Now open Devtools and click on device view.
3. Observe the scrollbar in the webpage in emulated view.

Actual : Two scroll bars are seen in emulated view.

Expected : Only one scroll bar should be seen in emulated view.

This is a regression issue broken in 'M-49'.

Manual Regression Range:
Good build : 49.0.2565.0
Bad build : 49.0.2568.0

Narrow bisect :
https://chromium.googlesource.com/chromium/src/+log/ab34a8ec1528bd2bad8a4566d39751d77e7bfa6e..9f5fa51c61d1d49d635eaba7f0dfdb9f26936651?pretty=fuller&n=50

Suspecting : r359993 ?