This tests that pages with plugins behave properly with the page cache. This includes:
-The plugin being destroyed upon navigation away from the page.
-The plugin being recreated upon restoring the page from the page cache.
-Plugin script objects accessed the first time the plugin was created are appropriately invalidated after the page has been restored from the page cache.
Unfortunately there is no reliable way to get affirmative confirmation that the plugin was destroyed upon navigation away from the page. For now we'll assume recreation means it had successfully been destroyed.