Implement "wait for connection" feature

src/debug.cc

Index: src/debug.cc
diff --git a/src/debug.cc b/src/debug.cc
index 2c4552effeabb5ab42abea5f91d97a9c7fe99329..fbe09391e27fabe4c9934adb79463a57288565ab 100644
--- a/src/debug.cc
+++ b/src/debug.cc
@@ -2483,7 +2483,24 @@ Handle<Object> Debugger::Call(Handle<JSFunction> fun,
 }
 
 
-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();