crash-reporter: Remove some dependency on /proc

Make the existence of a crashing process's /proc/<PID>/ directory optional
for all of crash_reporter, except for core2md.  In particular, have the
kernel pass the UID of the crashing process to crash_reporter in case the
"status" file is unavailable.

BUG=chromium-os:34385
TEST=Ran unittests and autotests
CQ-DEPEND=I6048d3eb84f8188bee6a755eaa010510f5d2459b

Change-Id: I62df52cab44cf1febc7ed3e55b75bcffa0daf524
Reviewed-on: https://gerrit.chromium.org/gerrit/34078
Commit-Queue: David James <[email protected]>
Reviewed-by: David James <[email protected]>
Tested-by: David James <[email protected]>
3 files changed