mw.Uri ignores keys in query string which are the name of a JavaScript Object prototype.
new mw.Uri( 'http://example.com/index.php?key=key&hasOwnProperty=hasOwnProperty&constructor=constructor&watch=watch' ).query
evaluates (on Firefox) to
Object { key="key" }
expected result
Object { key="key", hasOwnProperty="hasOwnProperty", constructor="constructor", watch="watch" }