Note: latest Canary is changing colors of various element interfaces (see https://bugs.chromium.org/p/chromium/issues/detail?id=805885, https://bugs.chromium.org/p/chromium/issues/detail?id=806607, https://bugs.chromium.org/p/chromium/issues/detail?id=806266) and it looks like more general problem.

Border around tab looks quite nice and potentially could be left (but can be closed then), from the second hand it's very possibly bug and app is not compliant with design docs now.

Tested the issue in Android and able to reproduce the issue. 

Steps Followed:
1. Launched the Chrome Browser with the flag #enable-chrome-home enabled.
2. Navigate to the URL which give color to omnibox bar. Eg.: www.facebook.com
3. Tap on tab switcher button and come back to the page.
4. Observe that borders of the tab are taken by the respective site color. 

Chrome versions tested:
66.0.3334.0(Canary)

OS:
Android 8.1.0

Android Devices:
Pixel XL

Using the per-revision bisect providing the bisect results,
Good Build - 66.0.3328.0 (530801)
Bad Build - 66.0.3331.0 (531794)  
(There were no installable builds between the above range for Pixel XL.)

You are looking for a change made after 531087(GOOD), but before 531088(BAD).

CHANGELOG URL:
The script might not always return single CL as suspect as some perf builds might get missing due to failure.
https://chromium.googlesource.com/chromium/src/+/5b7f1d69f1eb334e64dfff4b42fde77e37e98b80

From the CL above, assigning the issue to the owner concerned.

@mdjones:  Could you please look into the issue. Is it an intended change.

Please navigate to below link for log's and video--
go/chrome-androidlogs/806607

Note: 
1. This issue is not observed in Desktop.
2. Issue is similar to the  Issue 805885 

Thanks!

WAI. For future reference, Chrome Home is not supported after M65. One of the changed we are making is to support theme colors with the modern design.

 Issue 806607  has been merged into this issue.

 Issue 805885  has been merged into this issue.