Bug 1083092: Introduce |mozilla::ipc::SocketBase|, r=shawnjohnjr

The new class |SocketBase| contains the notification mechanism of
|SocketConsumerBase|. The latter still contains I/O methods.

ipc/unixsocket/UnixSocket.cpp

@@ -31,6 +31,7 @@ public:
 
   void                GetSocketAddr(nsAString& aAddrStr) const;
   SocketConsumerBase* GetConsumer();
+  SocketBase*         GetSocketBase();
 
   // Shutdown state
   //
@@ -157,6 +158,12 @@ UnixSocketConsumerIO::GetConsumer()
   return mConsumer.get();
 }
 
+SocketBase*
+UnixSocketConsumerIO::GetSocketBase()
+{
+  return GetConsumer();
+}
+
 bool
 UnixSocketConsumerIO::IsShutdownOnMainThread() const
 {