Bug 1059245 - Update tests and framework to use the new Browser app

So I've tested this and I tihnk it's a bug that the Marionette command is causing the keyboard to close. Marionette should be able to switch frame without triggering events like this. So we'll need to file a bug against Marionette, probably. 

I think it would be better not to change the signature of this method so let's put a hack in `search_panel.py` to tap the url bar again (to open the keyboard) and then tap enter key. We'll add a comment citing the Marionette bug as the reason for the hack and to remind us to remove it later.