Tip: For loading the real DOM we have https://github.com/borjasalguero/gaia/commit/f7f3cc2523946d5c5ba197dbfff82f632c7ae959#diff-b580022910a7b137d2dee789438e93b0R37, which comes from https://github.com/borjasalguero/gaia/commit/f7f3cc2523946d5c5ba197dbfff82f632c7ae959#diff-b580022910a7b137d2dee789438e93b0R20.
This let us to update our 'body' content given a `.html`. However in our case we are using the `import` of the HTML, so we need to add as well this `<link rel="import"...>` to the `head`. I've created the following https://github.com/borjasalguero/gaia/blob/f7f3cc2523946d5c5ba197dbfff82f632c7ae959/apps/system/test/unit/fxa_test/load_element_helper.js , so we can use the real HTML for testing :)