Using the per-revision bisect providing the bisect results,
Good build : 57.0.2979.0 (revision : 443120)
Bad build : 57.0.2980.0 (revision : 443474)

You are probably looking for a change made after 443240 (known good), but no later than 443241 (first known 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/+log/b103d6c66bbd7bebfe22affab2ea4930685a55bc..972a4d1ae26576f2a0cee1066a6ded6616538641

From the CL above, assigning the issue to the concern owner 

@jlebel - Could you please check whether this is caused with respect to your change, if not please help us in assigning it to the right owner.

Review-Url: https://codereview.chromium.org/2617583006

Thanks!

This bug is for macOS only. It works correctly on Windows and Linux.

This issue can be reproduced with any native sheet (like open dialog or save dialog) on macOS.

I think this is WAI. You shouldn't be able to interact with anything behind the native sheet until you've dismissed it by clicking on one of the buttons (that's the point of a browser-modal dialogue).

Is the bug that Chrome even opens a new tab in the background at all? Or that it focuses on the new tab?

cc'ing tapted@ who can close this out if it's WAI for native sheets

Also changing to just "Bug" because I think sheets on Mac have worked this way for a while (at least it's not tied specifically to the sync confirmation sheet).

After talking more with Jerome offline, I guess the bug here is that in the background, the newly created tab is getting focused. This is weird for sheets like the "save" panel, because it should be associated with the original tab on which it was opened.

Yeah the Cocoa `Edit Bookmark` dialog has done this since forever. It should be fixed, but it's low priority.

With respect to the label added: Needs-triage-Mobile, triaged the issue and below are the observations.

Unable to replicate the issue on Mobile device (Tablet and Handset) as the steps provided cannot be followed on it.

Devices Used:
=============
Device name: Nexus 6P (Handset)
Chrome version Used: Dev - 57.0.2984.3
Android Version: 7.1.1 / NMF26X

Device name : Samsung Galaxy Tab S2 (Tablet)
Chrome version Used: Dev - 57.0.2986.0
Android Version: 6.0.1 / MMB29K 

Reasons: 
========
1) Avatar icon is not displayed either on handset or tablet for chrome tabstrip
2) Signin overlay UI on mobile is different of what that is observed on desktop and the overlay text on mobile was unable to select or copied
3) Drag and drop functionality is not available on mobile devices.

P.S: Also tried by checking the option "Request desktop site", Cannot replicate the issue.

Yeah this isn't an issue on mobile.

This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

Sorry for the inconvenience if the bug really should have been left as Available. If you change it back, also remove the "Hotlist-Recharge-Cold" label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

[chrome mac triage]