Fixed some cctest flakiness on mac.

test/cctest/test-debug.cc

 // Copyright 2007-2008 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 4504 matching lines @@
   i::Socket::Setup();
 
   // Test starting and stopping the agent without any client connection.
   i::Debugger::StartAgent("test", kPort1);
   i::Debugger::StopAgent();
 
   // Test starting the agent, connecting a client and shutting down the agent
   // with the client connected.
   ok = i::Debugger::StartAgent("test", kPort2);
   CHECK(ok);
+  i::Debugger::WaitForAgent();
   i::Socket* client = i::OS::CreateSocket();
   ok = client->Connect("localhost", port2_str);
   CHECK(ok);
   i::Debugger::StopAgent();
   delete client;
 
   // Test starting and stopping the agent with the required port already
   // occoupied.
   i::Socket* server = i::OS::CreateSocket();
   server->Bind(kPort3);
@@ skipping 825 matching lines @@
       v8::Script::New(
           v8::String::New(
               "function runTest(mirror) {"
               "  return mirror.isString() && (mirror.length() == 5);"
               "}"
               ""
               "runTest;"))->Run());
   v8::Handle<v8::Value> result = run_test->Call(env->Global(), 1, &obj);
   CHECK(result->IsTrue());
 }