I wrote a Chrome extension a few years ago, and I completely don't remember how I did it. I'd like to make a new one, and I'm just having some trouble getting started. It needs to run every time someone visits a site at *.example.com. Certain pages (it's not really possible to tell which ones just by the URL) will return a large XML document rather than an HTML page. When a user visits a page on example.com that returns an XML document, the extension will parse through the XML and generate an HTML page to take its place. I can handle generating the HTML page from the XML, but how do I get the extension to start when someone visits the right page?