Chrome Version: 53.0.2785.101 Revision d68319683072a27031ebac6ac151e59f4190cab7-refs/branch-heads/2785@{#838} 
OS: Mac(10.10.5, 10.11.4)

What steps will reproduce the problem?
(1) Launch chrome, navigate to http://www.orimi.com/pdf-test.pdf
(2) Open dev tools window,click on 'Toggle device mode' icon.
(3) Middle click on Reload icon (same pdf page opened in NTP),observe the page

Actual: PDF page opened in zoomed view after middle clicking on pdf page.

Expected: PDF page should open properly.

This is a regression issue, broken in 'M-49', below is bisect info:

Good Build: 49.0.2565.0
Bad Build: 40.0.2568.0

Narrow Bisect:
https://chromium.googlesource.com/chromium/src/+log/ab34a8ec1528bd2bad8a4566d39751d77e7bfa6e..9f5fa51c61d1d49d635eaba7f0dfdb9f26936651?pretty=fuller&n=100

Suspecting: r359996 ?

Note: Issue is not seen on Windows and Linux OS.
 

Deleted: Actual_Video.mov 1.5 MB

Actual_Video.mov 1.5 MB Download

Deleted: Expected_Video.mov 1.4 MB

Expected_Video.mov 1.4 MB Download