Different treatment for htmlSafe in fastboot

[sdhull]

Reproduction:

// app/components/example-thing.js
  exampleCss: computed(function() {
    return [htmlSafe('.test > .thing'), ' { background-color: red; }'].join('\n');
  }),

{{!--  app/templates/components/example-thing.hbs  --}}
<style>{{exampleCss}}</style>
<div class='test'>
  <span class='thing'>hi hi hi</span>
</div>

(then of course render this component in your index template or application layout)

Expected:
The div .thing should have text 'hi hi hi' and red background, even with js turned off.

Actual:
The div .thing has a red background with js turned on (after app has initialized in the browser) but no red background with js turned off. The CSS selector gets escaped by fastboot (transforming > into >) while it does not get escaped by ember-in-the-browser.