Using the per-revision bisect providing the bisect results,
Good Build: 56.0.2907.0 (Revision : 429169)
Bad Build:  56.0.2908.0 (Revision : 429486)

You are probably looking for a change made after 429464 (known good), but no later than 429465 (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/be9e1f1ffc1e1d3287c7d994587446f9d7e703ee..63797594bc2bb93e645129b0c679081dc925ba5f

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

@dpapad - 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/2449663002

Thanks!

Everytime you press forward, a new search is happening for the letter 't' (based on your repro steps), which causes the icon to transition to the "spinner", but because the search finishes very quickly it transitions back to the search icon.

This behaviors seems reasonable, and not sure if there is anything to do here. Passing to @tbuckley for triaging.

Still able to reproduce the issue on Mac 10.12.1 using chrome version 57.0.2976.5.

tbuckley@ could you please check and confirm on this behaviour.

Thanks,

We could ensure that the spinner shows for some minimum amount of time (eg. transition in/out) so that it's less jarring.

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