Using the per-revision bisect providing the bisect results,
Good build: 57.0.2980.0 (Revision: 443474).
Bad build: 57.0.2981.0 (Revision: 443771).

You are probably looking for a change made after 443693 (known good), but no later than 443694 (first known bad).

CHANGE-LOG URL:
---------------------------------------
https://chromium.googlesource.com/chromium/src/+log/5489020f1edea26f4256621b874afebf7425fdf0..d5a7a73975d123369dab9784b2897467a31b0ab8


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

@spqchan: 
------------------
Could you please look into the issue, pardon me if it has nothing to do with your changes and if possible please assign it to concern owner.

Review-Url: https://codereview.chromium.org/2628703002

Note : Mac Specific issue.

Adding release block label, please undo if not the case.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ce00d1fcc3a2779d4db9771ca35513a416de9f9d

commit ce00d1fcc3a2779d4db9771ca35513a416de9f9d
Author: spqchan <spqchan@chromium.org>
Date: Thu Jan 26 18:21:16 2017

[Mac] Zoom Bubble Autoclosing Fix

With the new MD style the zoom bubble should autoclose, even if the
zoom decoration is pressed. Since the bubble isn't actually pointing
to the decoration, it should not stay opened, even when the the
decoration is pressed.

BUG= 682168 

Review-Url: https://codereview.chromium.org/2652893007
Cr-Commit-Position: refs/heads/master@{#446378}

[modify] https://crrev.com/ce00d1fcc3a2779d4db9771ca35513a416de9f9d/chrome/browser/ui/cocoa/location_bar/zoom_decoration.mm

[Auto-generated comment by a script] We noticed that this issue is targeted for M-57; it appears the fix may have landed after branch point, meaning a merge might be required. Please confirm if a merge is required here - if so add Merge-Request-57 label, otherwise remove Merge-TBD label. Thanks.

Your change meets the bar and is auto-approved for M57. Please go ahead and merge the CL to branch 2987 manually. Please contact milestone owner if you have questions.
Owners: amineer@(clank), cmasso@(bling), ketakid@(cros), govind@(desktop)

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

CL is merged: https://codereview.chromium.org/2674433002/

It's on the branch, but for something it's not showing up here?

Rechecked the issue on chrome version 57.0.2987.21 on MAC 10.12.2. Fix or merge is working as intended. ‘Zoom’ bubble vanishes when zoom level is set to default from omnibox.

Adding TE-Verified label.

Thanks.!