crash-reporter: Write out a magic string for Chrome crashes.

Also do some much needed code cleanup.

BUG=chromium:363660
TEST=emerge platform2

Change-Id: Ica9abfd854e2c77d970851805989c86a6a45fdee
Reviewed-on: https://chromium-review.googlesource.com/196764
Commit-Queue: Lei Zhang <thestig@chromium.org>
Tested-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
10 files changed