Using the per-revision bisect providing the bisect results,
Good build: 56.0.2908.0 (Revision: 429486).
Bad build: 56.0.2909.0 (Revision: 429737).

You are probably looking for a change made after 429657 (known good), but no later than 429658 (first known bad).
CHANGELOG URL:
  https://chromium.googlesource.com/chromium/src/+log/2a6cab73e4df91520c0cbcaacd9ee861dae7805b..f8c2ce99bb1ee0b1c6edb56d4194ecd886c76b8c

@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.

Thank You.

Able to reproduce the issue on Mac 10.11.6 using chrome version 57.0.2939.0.

spqchan@ could you please look into this issue.

Thanks,

I will look into it once I have the chance

Just to update, still able to reproduce this issue on Mac 10.12.2 using latest canary #57.0.2970.0.

Thanks...!!

Just to update, still able to reproduce this issue on Mac 10.12.2 using latest canary #57.0.2989.0.

Thanks!

@sdy, since you said you're taking some UI bugs, can you work on this? Feel free to reassign to me if you don't want to. Thanks!

This fix should also include a test to ensure that the spacing does not regress.

Friendly ping!!

Still we are able to reproduce the issue on mac 10.12.2 using latest Canary-58.0.3018.0.
sdy@Could you please look into this issue & update the thread.
Thank you!!

Ping received.

Just to an Update

Issue is still seen on mac 10.12.3 with latest canary(58.0.3026.0) 

sdy@: Could you please take a look at this and provide the latest update.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e6d41b083683603ccb42c1d01c0389d12c219cb8

commit e6d41b083683603ccb42c1d01c0389d12c219cb8
Author: spqchan <spqchan@chromium.org>
Date: Fri Mar 17 04:54:48 2017

[Mac] Added missing right padding for keyword hint

BUG= 668380 

Review-Url: https://codereview.chromium.org/2753103002
Cr-Commit-Position: refs/heads/master@{#457687}

[modify] https://crrev.com/e6d41b083683603ccb42c1d01c0389d12c219cb8/chrome/browser/ui/cocoa/location_bar/keyword_hint_decoration.mm

Your change meets the bar and is auto-approved for M58. Please go ahead and merge the CL to branch 3029 manually. Please contact milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), bhthompson@(ChromeOS), govind@(Desktop)

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

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ab1f101d05be92332f8c4a8532f6807e580c0568

commit ab1f101d05be92332f8c4a8532f6807e580c0568
Author: lgrey <lgrey@chromium.org>
Date: Mon Mar 20 15:13:20 2017

[Mac] Fix keyword hint spacing in RTL

BUG= 668380 

Review-Url: https://codereview.chromium.org/2755163002
Cr-Commit-Position: refs/heads/master@{#458064}

[modify] https://crrev.com/ab1f101d05be92332f8c4a8532f6807e580c0568/chrome/browser/ui/cocoa/location_bar/keyword_hint_decoration.mm

Note: Verified the above issue on latest Canary # 59.0.3047.0 on Mac OS (10.11.6, 10.12.1). The issue is fixed and working as intended.

This issue has been approved for a merge. Please merge the fix to any appropriate branches as soon as possible!

If all merges have been completed, please remove any remaining Merge-Approved labels from this issue.

Thanks for your time! To disable nags, add the Disable-Nags label.

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

This issue has been approved for a merge. Please merge the fix to any appropriate branches as soon as possible!

If all merges have been completed, please remove any remaining Merge-Approved labels from this issue.

Thanks for your time! To disable nags, add the Disable-Nags label.

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

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6d326645bf0aeb91943f247cc7f65b6531dd890a

commit 6d326645bf0aeb91943f247cc7f65b6531dd890a
Author: spqchan <spqchan@chromium.org>
Date: Mon Mar 27 17:20:09 2017

[Mac] Fix keyword hint spacing in RTL

BUG= 668380 

Review-Url: https://codereview.chromium.org/2755163002
Cr-Commit-Position: refs/heads/master@{#458064}
(cherry picked from commit ab1f101d05be92332f8c4a8532f6807e580c0568)

[Mac] Added missing right padding for keyword hint

BUG= 668380 

Review-Url: https://codereview.chromium.org/2753103002
Cr-Commit-Position: refs/heads/master@{#457687}
(cherry picked from commit e6d41b083683603ccb42c1d01c0389d12c219cb8)

Review-Url: https://codereview.chromium.org/2772383002 .
Cr-Commit-Position: refs/branch-heads/3029@{#427}
Cr-Branched-From: 939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}

[modify] https://crrev.com/6d326645bf0aeb91943f247cc7f65b6531dd890a/chrome/browser/ui/cocoa/location_bar/keyword_hint_decoration.mm