crash-reporter: log notification for chrome crashes

The standard crash collector logs a warning message every time it receives
a crash which makes reviewing system logs nice.  The chrome collector does
not do this which makes it a bit harder to track what the system is doing.
Add such a message to the chrome collector too.

BUG=chromium:415220
TEST=`cbuildbot amd64-generic-full` passes

Change-Id: I2b4c9990d99b780ed06d72be40b6ce5b95c1ee51
Reviewed-on: https://chromium-review.googlesource.com/218593


Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>