Failing tests:

DemoSessionMetricsRecorderTest.BrowserWindows
DemoSessionMetricsRecorderTest.AppTypes

First failing build: https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Mojo%20ChromiumOS/34243

Suspected cl: https://chromium-review.googlesource.com/1189711

Notes: tests added in Cl

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/84738a38f22b0bbc3cfe2a4f91186b768adaab84

commit 84738a38f22b0bbc3cfe2a4f91186b768adaab84
Author: Evan Stade <estade@chromium.org>
Date: Thu Sep 06 15:25:33 2018

Fix DemoSessionMetricsRecorderTest.BrowserWindows for Mash

In Mash, ShelfWindowWatcher tags unidentified windows with a
default App ID rather than leaving the App ID blank. Update the
test to reflect that.

Bug:  880595 
Change-Id: I844c4729b69c956fffd6a3acae1932f13e700158
Reviewed-on: https://chromium-review.googlesource.com/1208727
Commit-Queue: Evan Stade <estade@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589174}
[modify] https://crrev.com/84738a38f22b0bbc3cfe2a4f91186b768adaab84/ash/metrics/demo_session_metrics_recorder.cc
[modify] https://crrev.com/84738a38f22b0bbc3cfe2a4f91186b768adaab84/ash/shelf/shelf_window_watcher.cc
[modify] https://crrev.com/84738a38f22b0bbc3cfe2a4f91186b768adaab84/ash/shelf/shelf_window_watcher.h

Marking as fixed now that the unit tests are running on the main waterfall/CQ.