Fixed some cctest flakiness on mac.

src/debug-agent.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 29 matching lines @@
 
 
 // Debugger agent which starts a socket listener on the debugger port and
 // handles connection from a remote debugger.
 class DebuggerAgent: public Thread {
  public:
   explicit DebuggerAgent(const char* name, int port)
       : name_(StrDup(name)), port_(port),
         server_(OS::CreateSocket()), terminate_(false),
         session_access_(OS::CreateMutex()), session_(NULL),
-        terminate_now_(OS::CreateSemaphore(0)) {
+        terminate_now_(OS::CreateSemaphore(0)),
+        listening_(OS::CreateSemaphore(0)) {
     ASSERT(instance_ == NULL);
     instance_ = this;
   }
   ~DebuggerAgent() {
      instance_ = NULL;
      delete server_;
   }
 
   void Shutdown();
+  void WaitUntilListening();
 
  private:
   void Run();
   void CreateSession(Socket* socket);
   void DebuggerMessage(const v8::Debug::Message& message);
   void CloseSession();
   void OnSessionClosed(DebuggerAgentSession* session);
 
   SmartPointer<const char> name_;  // Name of the embedding application.
   int port_;  // Port to use for the agent.
   Socket* server_;  // Server socket for listen/accept.
   bool terminate_;  // Termination flag.
   Mutex* session_access_;  // Mutex guarging access to session_.
   DebuggerAgentSession* session_;  // Current active session if any.
   Semaphore* terminate_now_;  // Semaphore to signal termination.
+  Semaphore* listening_;
 
   static DebuggerAgent* instance_;
 
   friend class DebuggerAgentSession;
   friend void DebuggerAgentMessageHandler(const v8::Debug::Message& message);
 
   DISALLOW_COPY_AND_ASSIGN(DebuggerAgent);
 };
 
 
@@ skipping 32 matching lines @@
   static bool SendMessage(const Socket* conn,
                           const v8::Handle<v8::String> message);
   static int ReceiveAll(const Socket* conn, char* data, int len);
 };
 
 } }  // namespace v8::internal
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 #endif  // V8_DEBUG_AGENT_H_