Our current code is creating a name collision with DOM Promises implementation. const Promise = Cu.import... is preventing the DOM Promise object from landing. We should rename our Promise object (or use a destructuring assignment which I think will be more difficult to undo because of the multiple entries per file we'll have to search for) to clear this blockage. Baku suggested JSPromise. I would also entertain _Promise with varying numbers of underscores. This should not be done until after the merge on Monday, June 24, 2013.