:/

The fear I had was that this would fire too soon, before some of the resources in the page had finished loading. Obviously we want to catch as many as possible and then displayPageAction once.

But it seems from http://stackoverflow.com/questions/2149917/chrome-extensions-how-to-know-when-a-tab-has-finished-loading-from-the-backgr that this thing actually fires twice, and we really only want to catch the second time. So maybe add a `if (changeInfo.status === "complete")` in there.