Make the debugger completely unload when the debug event listener is unregist...

src/api.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 2875 matching lines @@
 }
 
 
 // --- D e b u g   S u p p o r t ---
 
 
 bool Debug::SetDebugEventListener(DebugEventCallback that, Handle<Value> data) {
   EnsureInitialized("v8::Debug::SetDebugEventListener()");
   ON_BAILOUT("v8::Debug::SetDebugEventListener()", return false);
   HandleScope scope;
-  i::Debugger::SetEventListener(i::Factory::NewProxy(FUNCTION_ADDR(that)),
-                                Utils::OpenHandle(*data));
+  i::Handle<i::Object> proxy = i::Factory::undefined_value();
+  if (that != NULL) {
+    proxy = i::Factory::NewProxy(FUNCTION_ADDR(that));
+  }
+  i::Debugger::SetEventListener(proxy, Utils::OpenHandle(*data));
   return true;
 }
 
 
 bool Debug::SetDebugEventListener(v8::Handle<v8::Object> that,
                                   Handle<Value> data) {
   ON_BAILOUT("v8::Debug::SetDebugEventListener()", return false);
   i::Debugger::SetEventListener(Utils::OpenHandle(*that),
                                 Utils::OpenHandle(*data));
   return true;
@@ skipping 112 matching lines @@
       reinterpret_cast<HandleScopeImplementer*>(storage);
   List<void**>* blocks_of_archived_thread = thread_local->Blocks();
   v8::ImplementationUtilities::HandleScopeData* handle_data_of_archived_thread =
       &thread_local->handle_scope_data_;
   Iterate(v, blocks_of_archived_thread, handle_data_of_archived_thread);
 
   return storage + ArchiveSpacePerThread();
 }
 
 } }  // namespace v8::internal