Chrome Version: 51.0.2686.0 Revision b3fd89db02212a4c8cd3c9f19632a2b2e0fe1f68-refs/heads/master@{#382218}(32/64 bit)
OS: All(win-7 Aero Enabled)

URL: https://chrome.google.com/webstore/detail/pdf-viewer/oemmndcbldboiebfnladdacbdfmadadm?hl=en 

What steps will reproduce the problem?
(1) Launch chrome,navigate to above url and click on 'ADD TO CHROME' button.
(2) Open pdf file(e.g.http://www.orimi.com/pdf-test.pdf),click on extension icon and observe.

Spacing issue is seen after clicking on extension icon.

No such unwanted space should seen after clicking on extension icon.

This is a regression issue broken in 'M-51',below is manual bisect range:

Good Build: 51.0.2681.0
Bad Build: 51.0.2682.0

Narrow Bisect: https://chromium.googlesource.com/chromium/src/+log/dff8eb21c3e4882bb0c522d83a46bb16d8a2643a..3242e5d006f531af516d464c7084dde7e1346f0d?pretty=fuller&n=10

Suspecting: r381668

@tkent: Please help me to assign this issue if your change is not cause for it.
 

Deleted: Actual_PDF.mp4 447 KB

Actual_PDF.mp4 447 KB Download

Deleted: Expected_PDF.mp4 344 KB

Expected_PDF.mp4 344 KB Download