Reapply "wait for connection" feature implementation

src/debug.cc

 // 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 2465 matching lines @@
   }
 
   static const int kArgc = 2;
   Object** argv[kArgc] = { exec_state.location(), data.location() };
   Handle<Object> result = Execution::Call(fun, Factory::undefined_value(),
                                           kArgc, argv, pending_exception);
   return result;
 }
 
 
-bool Debugger::StartAgent(const char* name, int port) {
+static void StubMessageHandler2(const v8::Debug::Message& message) {
+  // Simply ignore message.
+}
+
+
+bool Debugger::StartAgent(const char* name, int port,
+                          bool wait_for_connection) {
+  if (wait_for_connection) {
+    // Suspend V8 if it is already running or set V8 to suspend whenever
+    // it starts.
+    // Provide stub message handler; V8 auto-continues each suspend
+    // when there is no message handler; we doesn't need it.
+    // Once become suspended, V8 will stay so indefinitely long, until remote
+    // debugger connects and issues "continue" command.
+    Debugger::message_handler_ = StubMessageHandler2;
+    v8::Debug::DebugBreak();
+  }
+
   if (Socket::Setup()) {
     agent_ = new DebuggerAgent(name, port);
     agent_->Start();
     return true;
   }
 
   return false;
 }
 
 
@@ skipping 228 matching lines @@
 
 
 void LockingCommandMessageQueue::Clear() {
   ScopedLock sl(lock_);
   queue_.Clear();
 }
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 } }  // namespace v8::internal