[tab_under] Log block error to console

We already show some UI, but devs should probably be able to see the
chromestatus entry and find their way to the crbug.

We could also probably add a warning at some point, but I will wait till
the intent gets approval before logging something that isn't behind a
feature flag.

Bug: 661629
Change-Id: I3cb86f393b1ddda1fa5f5596823d1833b10814e9
Reviewed-on: https://chromium-review.googlesource.com/731967
Commit-Queue: Charlie Harrison <csharrison@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#510710}
3 files changed