Separate out IPC::Message::Sender and channel::Listener into a separate class.

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 c71370fbc8964d1a81b53312366bd2d0cbab7b0b..b4e7e17a282773e523302d80b2bbc24ded505832 100644
--- a/ipc/ipc_channel_posix.h
+++ b/ipc/ipc_channel_posix.h
@@ -54,7 +54,7 @@ class Channel::ChannelImpl : public internal::ChannelReader,
  public:
   // Mirror methods of Channel, see ipc_channel.h for description.
   ChannelImpl(const IPC::ChannelHandle& channel_handle, Mode mode,
-              Listener* listener);
+              ChannelListener* listener);
   virtual ~ChannelImpl();
   bool Connect();
   void Close();