Fixing bug 318270. Fix refcount problem in ns4xPluginInstance::GetDOMWindow() that lead to crashes due to window objects being deleted too quickly. r=mrbkap@gmail.com, r+sr=bzbarsky@mit.edu

modules/plugin/base/src/ns4xPluginInstance.cpp

@@ -957,7 +957,10 @@ ns4xPluginInstance::GetDOMWindow()
     return nsnull;
   }
 
-  return doc->GetWindow();
+  nsPIDOMWindow *window = doc->GetWindow();
+  NS_IF_ADDREF(window);
+
+  return window;
 }
 
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