Revert 80604 - Revert 80602 - Limit access to named IPC channels with SO_PEERCRED, not file permissions.BUG=TEST=Run Chrome & configure a service, to get the service process to start.  Close Chrome and run a copy as a different user, but from the same user-data-dir.  New Chrome should not be able to communicate with the service process.Review URL: http://codereview.chromium.org/6631002TBR=wez@chromium.orgReview URL: http://codereview.chromium.org/6806006
TBR=wez@chromium.org
Review URL: http://codereview.chromium.org/6806007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@80606 0039d316-1c4b-4281-b951-d872f2087c98

• ipc/ipc_channel.h[diff]
• ipc/ipc_channel_posix.cc[diff]
• ipc/ipc_channel_posix.h[diff]
• ipc/ipc_channel_proxy.cc[diff]
• ipc/ipc_channel_proxy.h[diff]