Remove the partially completed code for remote IsolateMirrors and

runtime/vm/message_handler.h

Index: runtime/vm/message_handler.h
===================================================================
--- runtime/vm/message_handler.h	(revision 7926)
+++ runtime/vm/message_handler.h	(working copy)
@@ -69,6 +69,9 @@
   // ------------ 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; }
+
   // Posts a message on this handler's message queue.
   void PostMessage(Message* message);