Visit URLs in a hidden tab/window invisible to user.
In FF, we use the page-worker API for this. In Chrome we may need to create and manage an iframe on the background page (though I really hope there's a nicer way to do this). Another option might be this.
Step 1: Visit a URL and load the returning page in a hidden tab/window/iframe
Step 2: Store a list of URLs to be visited, trying each one on a timer (only one should be in-process at a time)
Step 3: Handle failures -- on failure, the URL should be visited again after a pause; after the 3rd failure, give-up
Step 4: Harden -- disable JS, Flash, plugins, popups, etc on returned page
Visit URLs in a hidden tab/window invisible to user.
In FF, we use the page-worker API for this. In Chrome we may need to create and manage an iframe on the background page (though I really hope there's a nicer way to do this). Another option might be this.