Add locker support to DebugMessageDispatchHandler

src/debug.cc

Index: src/debug.cc
diff --git a/src/debug.cc b/src/debug.cc
index fbe09391e27fabe4c9934adb79463a57288565ab..6b01d98cf01a784b56c9da6e6c6fddfb191e2383 100644
--- a/src/debug.cc
+++ b/src/debug.cc
@@ -2438,8 +2438,16 @@ void Debugger::ProcessCommand(Vector<const uint16_t> command,
     StackGuard::DebugCommand();
   }
 
-  if (Debugger::debug_message_dispatch_handler_ != NULL) {
-    Debugger::debug_message_dispatch_handler_();
+  {
+    // TODO: Lock only optionally
+    LockParameters lock_params;
+    Locker lock(&lock_params);
+    if (lock_params.successfully_relaied) {
+    } else {
+      if (Debugger::debug_message_dispatch_handler_ != NULL) {
+        Debugger::debug_message_dispatch_handler_();
+      }
+    }
   }
 }