Bug 1411578 and descendants prevented us from crashing when there was a write error to MutableBlobStorage. When such an error surfaces though, we delete the currently gathered file, discarding any material recorded thus far. Users might instead want to salvage what was already recorded, so we should consider retaining the blob and presenting it to the application. Even if the disk is full the user might have another disk to save it onto, or the application perhaps has a server it can upload the recording to.