Adding the 'non client decor view' to free floating windows

This patch adds a new free floating window non client decor view which
has:
- Two buttons (maximize and close) as it meets our current UX design
- A Shadow which changes size with focus
- It's own view as preparation for the thread distributed drawing and
  user interaction handling (resize handles, etc)

Missing is at this point:
- The button functionality itself.
- Changing/removing decors based on window type (once the needed
  patches land.

bug: 21738666
bug: 21739152
Change-Id: I6e41f2a7470256cee7bae35029d7e8c43fb235dd