crash-reporter: avoid deadlock if dbus-daemon is hanging

Change-Id: I40ba7fb556217bf0bea156e0496145d7195a1229

BUG=7783
TEST=sudo pkill -STOP dbus-daemon;sleep 100&ill -SEGV $!;pgrep crash_reporter shows crash_reporter finished dumping sleep, even though dbus-daemon is unreachable.  Also ran UserCrash and CrashSender.

Review URL: http://codereview.chromium.org/3976001
1 file changed
tree: 69528452cddc00261eb1e05ded2f486427dd760b
  1. crash_reporter/