Need to establish a process for how we are going to use x-tags in the next version of the templates. I think we should look at Polymer to see how they are doing it, just for some outside ideas. Most likely we'll just bundle a bunch of tags into a single js file, and we need to figure out which tags those are.
I think this bug might be similar to a few other ones, but sole has gone ahead and rebuilt the list-detail template with x-tags which is awesome. We have a basic process in place now, but I want to keep this bug open to remind us to research better solutions for bundling x-tags.
I think we are past the research phase; Leon has made a list of components that will be built: https://github.com/mozilla/app-components. bug 876028 has detailed discussion of how we are going to organize and deploy these deployments. I have looked at Polymer and the current x-tags to figure out how we should rebuild the current templates, with the conclusion that we need to really need to focus on a few components like scrollbox and made them work (too many tags are still in alpha phase). Future will be represented by smaller bugs.