Changed structure such that background maintains a map of all tabs by id and their currently blocked state. This allows us to request the currently blocked site simply by calling afunction on the bakcground page.
Added a onTabReplaced handler to the background.js page. This updates the map when the tabId changes, allowing us to maintain a consistent mapping of tabs to blocked status.
Fully functional and styled. Could still use an options page. Could probably use a lot of efficiency improvement... onBeforeRequest gets called tens of times for a single page load. Still needs commenting.