Change DesktopRootWindowHostTizen from DesktopRootWindowHostXwalk.

After this CL, only Tizen(tizenos=1) uses DesktopRootWindowHostTizen. Desktop
linux uses DesktopRootWindowHostX11.
We have changed and will change DesktopRootWindowHostTizen only for Tizen, so
only Tizen should use this class.