Alter behavior of getFirstPartyURI and consumers
Our mozIFirstPartyUtil.getFirstPartyURI should log to the error console and emit a failure code if it either fails to get a URI, or if that URI has a NULL hostname. This will simplify the code that makes use of the API.
If the API call fails for ImageCache consumers, we should load but not cache the image (if possible). If the API call fails for DOM Storage, the DOM Storage calls should probably also fail. For the canvas, we should also fail the calls (See also #7265 (closed) for related canvas changes).