Bug 1075306 - Implement InputWindow (inherits from AppWindow)

- Instances of InputWindow replaces those iframes we were keeping in InputFrameManager.
- InputAppTransitionManager has been eliminated, in favor of already-built AppTransitionController that works closely with AppWindow.
- The coupling of KeyboardManager, InputFrameManager and InputWindows shall be resolved in a following bug where we'll implement InputWindowManager.
- Flow of showing/hiding/reusing/switching input apps & layouts has been streamlined.
Well, even the sub-component is not there, I still see div.chrome inside the div.inputWindow. There is text ‘Search the web’ in div.chrome > div.controls > div.urlbar > div.title, which might be seeable in a quickflash when we go back to homescreen from an app with keyboard open.