Chrome Version:54.0.2799.0 (Official Build)8acb9d5f2f71c3df8e64b13ee321a9d194e89785-refs/heads/master@{#405947} 64 bit
OS: MAC PRO (10.10.5) (10.11.4)

Test url:
1.https://chrome.google.com/webstore/detail/mount-everest-1440%2B-x-900/bnlehkcgeooloejojajmeolmhiaeoiej?hl=en
2.https://chrome.google.com/webstore/detail/facebook-app-launcher/dihbebhmaoagdpbcnfedokpfkkgmmpgc?hl=en

Pre-condition:
1. Install “Mount-everest” theme using test url 1.
2. Add ‘Facebook App Launcher’ app using test url 2.

What steps will reproduce the problem?
1. Launch chrome and navigate to chrome://apps/,click on ‘Facebook App Launcher’ app icon.
2. On App window, right click and select ‘Inspect’ option from context menu.
3. Observe.

Actual: Background colour of theme is seen while opening devtools window.
Expected: Theme background colour should not be seen while opening the devtools window.

This is regression issue, broken in ‘M 51’ and below is narrow bisect:
https://chromium.googlesource.com/chromium/src/+log/8526ab53583e2cc6390fb4693132b151d2481ea1..1ba5ac190a8a46a6ac5b8f1b06bcb66ec6eb967e?pretty=fuller&n=1000

Suspecting: r382955

Good build:51.0.2688.0
Bad build:51.0.2689.0

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

Deleted: Actual.mov 3.5 MB

Actual.mov 3.5 MB Download