bug 1048752 followup 2 - another Windows non-unified build fix. no_r=me, bustage fix

accessible/windows/msaa/nsWinUtils.cpp

@@ -16,6 +16,7 @@
 #include "nsIArray.h"
 #include "nsIDocument.h"
 #include "nsIDocShellTreeItem.h"
+#include "nsIDOMElement.h"
 #include "nsXULAppAPI.h"
 
 using namespace mozilla;