Oshima, Please reassign if you are not the right owner. This is found in 51. Does this also affect 50 since you called it beta blocker?

I haven't seen this on m50 yet. I added RB-beta because we should avoid releasing m51 beta in this state. I'll discuss this albert@ when he's back.

+jamescook@, in case he knows recent mus related change that might have affected this.

+xdai@ who looked into focus issue recently.

+xiyuan +afakhry who worked on login screen stuff recently.

+jdufault@ also working on lock recently.

I don't know of any recent mus stuff that touched login, but I'm not involved in that many code reviews yet. +msw@ -- Do you know if we touched anything with ash containers recently? ash focus?

Any focus/activation related change might have affected this. I'll look into a bit more later this week.

Speaking of ash focus rules change, not sure if one of my recent CLs related: https://codereview.chromium.org/1753473003 

I've landed https://codereview.chromium.org/1811113003/ recently which affects the lock screen, though I'd be extremely surprised if it was the cause of this issue. I have another CL which will refactor the lockscreen but it's waiting in CR.

My most suspect change would be making ShelfTooltipManager a root window pre-target handler:
https://codereview.chromium.org/1828133004/diff/140001/ash/shelf/shelf_tooltip_manager.cc
I doubt that's it, but can't think of other CLs that could trigger this. Is it easy to bisect?

This just happened to me this morning. I couldn't find repro step yet, but the security key was flashing when this was happening, so I wonder if the dialog is stealing focus.

Clicking didn't help so none of these changes may be related. 

Just an update: I haven't seen this sine last update. 

Google Chrome	51.0.2699.0 (Official Build) dev (64-bit)
Platform	8155.0.0 (Official Build) dev-channel stumpy

I'll reopen if I see this again.