Bug 584864 - MessageManager's LoadFrameScript runs in Chrome windows, r=smaug

content/base/src/nsFrameLoader.cpp

@@ -1888,6 +1888,11 @@ nsFrameLoader::EnsureMessageManager()
   if (NS_FAILED(rv)) {
     return rv;
   }
+
+  if (!mIsTopLevelContent) {
+    return NS_OK;
+  }
+
   if (mMessageManager) {
 #ifdef MOZ_IPC
     if (ShouldUseRemoteProcess()) {