Mixing chrome.i18n (internationalization method) into templates
I doubt performance will take much of a hit by passing chrome.i18n into your templates, but I still don't think you should do it.

Templates should be solely for visualising data where possible, sometimes this requires a small amount of logic, but you should keep it out whenever possible. I would much rather see this:

var i18n = chrome.i18n;

...

templateHelpers: function () {
    return {
        hdMessage: i18n.getMessage('hd'),
        instant: this.instant
    };
}


-

&lt;% if( video.get('highDefinition') ) { %&gt;
    &lt;%= hdMessage %&gt; · 
&lt;% } %&gt;


In the long run this prevents your templates from being cluttered with internationalisation specific code, which will also be useful if you ever need to change the library.