Chrome Version : 55.0.2869.0 (Official Build) 333a7dd429e44a6562112fc29c667474fa2e92f9-refs/heads/master@{#420536} (64-bit)
OS: Mac(10.10.5)(10.11.5)

What steps will reproduce the problem?
1. Launch chrome, open NTP, click on wrench menu and open task manager.
2. Click on the last ‘Task’ entry seen in task manager and press ’Shift + Tab’ key twice such that blue focus ring is seen on that task.
3. Now click on second last ‘Task’ entry and click on ‘End Process’ button, observe the blue focus ring. 

Actual : Unwanted blue focus ring is seen on killing task.
Expected : No such blue focus ring should be seen on killing task.

This is a regression issue broken in ‘M-46’, below is the Manual Regression and Narrow Bisect info. 
Good build: 46.0.2479.0
Bad build: 46.0.2480.0

Narrow Bisect : 
https://chromium.googlesource.com/chromium/src/+log/69a68c76ec6d27e8b27eeb0851bbc3247b700a3b..87c301252978ea7b06b95b1ec03f51e4309bd0bc?pretty=fuller&n=10000

Blink CL : 
https://chromium.googlesource.com/chromium/blink/+log/f2395b6..d47b538?pretty=fuller&n=10000

Suspecting: r342870 ? from Narrow Bisect

@erikchen : Please help to re-assign if your change is not the cause for this issue.

Note : This is mac specific issue and not reproducible on Windows and Linux OS.
 

Deleted: Actu_task_manager.png 62.0 KB

	Actu_task_manager.png 62.0 KB View Download

Deleted: Expected_task_manager.mov 4.0 MB

Expected_task_manager.mov 4.0 MB Download