Add additional logging to verify if test times out due to missed events
Several recent flaky test issues were due to crashes that were
unreported, making it appear that the test had timed out. This change
adds additional logging, including a heartbeat message every second,
that should help to diagnose if the test actually times out (as there
will be lots of heartbeat messages logged).
BUG=480750
TEST=making the tests fail results in lots of heartbeat messages
Review URL: https://codereview.chromium.org/
1292963002
Cr-Commit-Position: refs/heads/master@{#344425}