GitLab

When remote debugging port set to 0, allow web_engine_shell to find available port to use.
Allow web_engine_shell to log the remote debugging port (if turned on).

Bug: 1014642
Change-Id: I7e7b98f10eb8ea0aa17c1a4761bbb50bf9d32dba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1984626
Commit-Queue: Chong Gu <chonggu@google.com>
Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#729566}