As part of restyling searches, we need to ensure that search urls which were filled with a purpose parameter are also updated.

For example, we use the MozParams in Bing, if a search is made from the context menu, and that search is restyled for use in the address bar, then we'll be sending the wrong purpose if we use it - we should change the url to use the purpose parameters associated with the address bar.

Note: this bug replaces bug 1063530 which had the same intention, but the description was unclear.