Narrow bisect:
https://chromium.googlesource.com/chromium/src/+log/17ab3580c8d3081a1c728eb33d6e5f35684fd5a5..3644e8c55d11a9b4693aa20001b116cdbca266e2?pretty=fuller&n=10

Suspecting: r395828 ?

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

Marking the above issue as RB-Stable as this is a recent regression.

Thank you!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/77463dee8d2a75837f207cc8d8af599a2ac43120

commit 77463dee8d2a75837f207cc8d8af599a2ac43120
Author: takumif <takumif@chromium.org>
Date: Wed Sep 28 20:45:14 2016

[MR UI] Make paper-items the only selectable elements in cast modes list

Currently when you are tabbing through the cast mode selection view in the MR
dialog, you cannot highlight the casting options, because the "Share your
screen" text gets selected instead (which doesn't change its appearance when
selected). It's not clear where the selection went, or that you can then
highlight the cast modes by pressing up/down arrow keys. This change makes
only the cast modes selectable.

BUG= 614948 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2369223002
Cr-Commit-Position: refs/heads/master@{#421634}

[modify] https://crrev.com/77463dee8d2a75837f207cc8d8af599a2ac43120/chrome/browser/resources/media_router/elements/media_router_container/media_router_container.html