Revert 270173 "Remove SCM_CREDENTIALS fallback code from breakpad"
build break: http://build.chromium.org/p/chromium.linux/builders/Linux%20Tests%20%28dbg%29%281%29%2832%29/builds/5169/steps/browser_tests/logs/CDMExpectedCrash
> Remove SCM_CREDENTIALS fallback code from breakpad
>
> Since r266618, we require SCM_CREDENTIALS to work correctly across PID
> namespaces, and refuse to run on kernels where it doesn't.
>
> NOTRY=true
>
> Review URL: https://codereview.chromium.org/
283643004
TBR=mdempsky@chromium.org
Review URL: https://codereview.chromium.org/
275913003
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270277 0039d316-1c4b-4281-b951-d872f2087c98