Bug 1028691 - [Collection app] Background images sometimes in poor quality

http://bugzil.la/1028691

Since the collection.background can be updated by two processes - a) Collection create b) Collection view, the former requests a 170x170 image which is then displayed as the Collection content bg. Then gets overwritten with the full size bg.

The fix simply keeps a record if the current bg image is full sized or not and displays only if it is.
In the past this was due to how firefox handled window.onerror calls... Mocha knew it timed out but not why the error occurred and so would report nothing.