Mojo: First stab at making MessagePipes work across OS pipes.

mojo/system/message_pipe.h

Index: mojo/system/message_pipe.h
diff --git a/mojo/system/message_pipe.h b/mojo/system/message_pipe.h
index bb2f4ff0a7d8366551c988333d02c5bfaef49261..67f99d2f584e1ed7ebf717c8f6311ac923ae8218 100644
--- a/mojo/system/message_pipe.h
+++ b/mojo/system/message_pipe.h
@@ -6,15 +6,18 @@
 #define MOJO_SYSTEM_MESSAGE_PIPE_H_
 
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/synchronization/lock.h"
 #include "mojo/public/system/core.h"
 #include "mojo/public/system/system_export.h"
+#include "mojo/system/message_in_transit.h"
 
 namespace mojo {
 namespace system {
 
+class Channel;
 class MessagePipeEndpoint;
 class Waiter;
 
@@ -32,6 +35,9 @@ class MOJO_SYSTEM_EXPORT MessagePipe :
   // |LocalMessagePipeEndpoint|s.
   MessagePipe();
 
+  // Gets the other port number (i.e., 0 -> 1, 1 -> 0).
+  static unsigned GetPeerPort(unsigned port);
+
   // These are called by the dispatcher to implement its methods of
   // corresponding names. In all cases, the port |port| must be open.
   void CancelAllWaiters(unsigned port);
@@ -54,10 +60,26 @@ class MOJO_SYSTEM_EXPORT MessagePipe :
                        MojoResult wake_result);
   void RemoveWaiter(unsigned port, Waiter* waiter);
 
+  // This is used internally by |WriteMessage()| and by |Channel| to enqueue
+  // messages (typically to a |LocalMessagePipeEndpoint|). Unlike
+  // |WriteMessage()|, |port| is the *destination* port. Takes ownership of
+  // |message|.
+  MojoResult EnqueueMessage(unsigned port, MessageInTransit* message);
+
+  // These are used by |Channel|.
+  void Attach(unsigned port,
+              scoped_refptr<Channel> channel,
+              MessageInTransit::EndpointId local_id);
+  void Run(unsigned port, MessageInTransit::EndpointId remote_id);
+
  private:
   friend class base::RefCountedThreadSafe<MessagePipe>;
   virtual ~MessagePipe();
 
+  // Used by |EnqueueMessage()| to handle control messages that are actually
+  // meant for us.
+  MojoResult HandleControlMessage(unsigned port, MessageInTransit* message);
+
   base::Lock lock_;  // Protects the following members.
   scoped_ptr<MessagePipeEndpoint> endpoints_[2];