Currently it's hard to reason about the hung tests on worker processes.
This adds simple output when we're trying to kill a hung process.

Change-Id: Iae5e14dac70a8149c074043dd00cbf10e4d5f3de
Reviewed-on: https://chromium-review.googlesource.com/712455Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48460}