Instrument some of the exit paths likely to suffer hangs.

This is temporary instrumentation to try and narrow down the area
and mode where Chrome is (likely) hanging on logoff/restart.

TBR=mpearson@chromium.org,erikwright@chromium.org

BUG=412384

Review URL: https://codereview.chromium.org/796963002

Cr-Commit-Position: refs/heads/master@{#308222}
7 files changed