chore(style): fix coding style to use more dart idioms
chore(mock): Converting mock's Logger to use ListBase

It was using noSuchMethod and mirrors, both of which have the potential to bloat dart2js code size. This change may not have any real-world impact given the number of other places which also hit mirrors and NSM, but it seems good to remove the gratuitous use of these APIs.
feat(cookies): Basic Cookies service/wrapper over BrowserCookies