Allowing the client to create its own pipe name string caused a race
between client and server. Instead, in this mode, the server now creates
the pipe name along with a pipe, and returns it to its client via a
--handshake-handle. This guarantees that by the time the client gets the
pipe name, the server has already created it.
Ephemeral mode is now implied by --handshake-handle. The --persistent
option is gone. --persistent mode is enabled when using --pipe-name.
BUG=crashpad:69
R=scottmg@chromium.org
Review URL: https://codereview.chromium.org/1432563003 .