Ignore V8's message handler that is invoked while we're initializing a window

Source/bindings/v8/V8Initializer.cpp

Index: Source/bindings/v8/V8Initializer.cpp
diff --git a/Source/bindings/v8/V8Initializer.cpp b/Source/bindings/v8/V8Initializer.cpp
index ed0edf1f51c7e0dc5a4926ffb171b390d884ed60..98dce3b8fc1fd36669dcce3b4cae9029b16d528b 100644
--- a/Source/bindings/v8/V8Initializer.cpp
+++ b/Source/bindings/v8/V8Initializer.cpp
@@ -85,6 +85,13 @@ static void reportFatalErrorInMainThread(const char* location, const char* messa
 
 static void messageHandlerInMainThread(v8::Handle<v8::Message> message, v8::Handle<v8::Value> data)
 {
+    ASSERT(isMainThread());
+    // It's possible that messageHandlerInMainThread() is invoked while we're initializing a window.
+    // In that half-baked situation, we don't have a valid context nor a valid world,
+    // so just return immediately.
+    if (DOMWrapperWorld::windowIsBeingInitialized())
+        return;
+
     v8::Isolate* isolate = v8::Isolate::GetCurrent();
     // If called during context initialization, there will be no entered window.
     DOMWindow* enteredWindow = enteredDOMWindow(isolate);