1. Create a port when a debugger object is created for an isolate, use this

vm/message_handler.h

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_MESSAGE_HANDLER_H_
 #define VM_MESSAGE_HANDLER_H_
 
 #include "vm/message.h"
 #include "vm/thread.h"
 #include "vm/thread_pool.h"
@@ skipping 54 matching lines @@
   virtual void CheckAccess();
 #endif
 
  protected:
   // ------------ START PortMap API ------------
   // These functions should only be called from the PortMap.
 
   // Does this message handler correspond to the current isolate?
   virtual bool IsCurrentIsolate() const { return false; }
 
+  // Return Isolate to which this message handler corresponds to.
+  virtual Isolate* GetIsolate() const { return NULL; }
+
   // Posts a message on this handler's message queue.
   void PostMessage(Message* message);
 
   // Notifies this handler that a port is being closed.
   void ClosePort(Dart_Port port);
 
   // Notifies this handler that all ports are being closed.
   void CloseAllPorts();
 
   // Returns true if the handler is owned by the PortMap.
@@ skipping 38 matching lines @@
   StartCallback start_callback_;
   EndCallback end_callback_;
   CallbackData callback_data_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageHandler);
 };
 
 }  // namespace dart
 
 #endif  // VM_MESSAGE_HANDLER_H_