Use restoreProcessorState in integration.js

[simon]

We discussed this briefly in #1770, but it's worth making an independent ticket for it. I'd like to do this, since it will speed things up and simplify the logic, but I'm not yet sure whether we want this for 2.1 or not, since we need to get 2.1 out the door around the same time as Firefox 4, which is supposedly nearing completion, although they continue to make last minute Zotero-killing API changes.