Implement IPC::ChannelFactory, a class that accept()s on a UNIX socket.

ipc/ipc_channel_posix.h

Index: ipc/ipc_channel_posix.h
diff --git a/ipc/ipc_channel_posix.h b/ipc/ipc_channel_posix.h
index 38e14ef14b684f5fc7f76a1386b4a4aae91ff403..64b8f611c729774e5a7fff0e3740aa28a4f4530f 100644
--- a/ipc/ipc_channel_posix.h
+++ b/ipc/ipc_channel_posix.h
@@ -194,12 +194,6 @@ class Channel::ChannelImpl : public internal::ChannelReader,
   DISALLOW_IMPLICIT_CONSTRUCTORS(ChannelImpl);
 };
 
-// The maximum length of the name of a pipe for MODE_NAMED_SERVER or
-// MODE_NAMED_CLIENT if you want to pass in your own socket.
-// The standard size on linux is 108, mac is 104. To maintain consistency
-// across platforms we standardize on the smaller value.
-static const size_t kMaxPipeNameLength = 104;
-
 }  // namespace IPC
 
 #endif  // IPC_IPC_CHANNEL_POSIX_H_