1. Refactor the interfaces of the slider out side the ToggleSlider class.
2. BrightnessController now takes in only an IToggleSlider interface instead of
the view.
Bug: 28172423
Change-Id: Iff463a30e149f17795ccaffca66040d64f44a643
(cherry picked from commit 89c0cb853175c66769d287b8d6cf82c7166e0e6e)
3b0f892c8f