Right. We reuse the interpreter for different pages in the same part, hence detach happens pretty rarely. Accordingly, re-add the clearInterpreter hook from KJSProxy. For now it's only used for a sanity check. One could also kill the old documents on it. I am not sure which is right --- killing them can be annoying since all the tabs disappear; if one doesn't kill them, stuff leaks ifthe debugger is on.