Bug 1093128 - Fix checking for the viewer to open when the user clicks a...

... link to protected content
1. This code originates from System App. I would suggest sending patch to System App.
2. In real devices, we use `app://` rather than `http://` or `https://` to represent app URL. So hard-coding `http` and `https` wouldn't work as expected I think.
3. Activity needs permission higher than installed app, and I'm not quite sure how to produce such installable app since they need to be qualified by Marketplace first... But I'm not quite sure about this.