Add support for crashpad integration in linux-ish clients

This CL implements crash/content/app/crashpad.h for linux but does not
migrate any clients from breakpad to crashpad.

Bug: crashpad:30
Change-Id: I00587795331d39d00c98f36949735c43d3e2e9a4
Reviewed-on: https://chromium-review.googlesource.com/972183
Commit-Queue: Joshua Peraza <jperaza@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547336}
10 files changed