mac: Add a mode to crashpad_handler to run from launchd

mac: Add a mode to crashpad_handler to run from launchd

By invoking crashpad_handler with --mach-service instead of
--handshake-fd, the handler will run as a well-behaved launchd job. The
launchd job may be as a launch agent or launch daemon, or be submitted
to launchd by on_demand_service_tool.

BUG=crashpad:25
R=rsesek@chromium.org

Committed: https://chromium.googlesource.com/crashpad/crashpad/+/809affe7930b4858ab2e84fbb4f6a423a3fcbe8e

[Mark Mentovai, 2015-11-02 19:30:25]

mark@chromium.org changed reviewers:
+ rsesek@chromium.org

[Mark Mentovai, 2015-11-03 14:11:23]

I want to move the signal handler out into main.cc to resolve some racy
behavior: in patch sets 1-3, the signal handler is set up after the upload
thread begins, and it’s torn down before the upload thread ends.

[Robert Sesek, 2015-11-03 16:03:13]

LGTM

[Robert Sesek, 2015-11-03 16:03:41]

On 2015/11/03 16:03:13, Robert Sesek wrote:
> LGTM

(though if you want to do the signal handler thing in this CL, that's fine too)

[Mark Mentovai, 2015-11-04 00:20:18]

I’ll just check this in as-is and fix up the signal handling in a follow-up.
Then you don’t have to keep looking at the same thing repeatedly.

[Mark Mentovai, 2015-11-04 00:20:34]

Committed patchset #4 (id:60001) manually as
809affe7930b4858ab2e84fbb4f6a423a3fcbe8e (presubmit successful).