WM: Parent SurfaceView to a new bounds surface

Fixes a couple of issues seen with PiP animations.
1. SurfaceView expands over the parent bounds.
2. SurfaceView and/or its background surface draws over the surface inset region of the parent.

Creates a child surface in ViewRootImpl that will crop any region outside its surface bounds after
adjusting for surface insets. Changed SurfaceView to parent to this new surface.

Test: manually run through PiP animations for Maps and YouTube.
Test: go/wm-smoke
Change-Id: Ib4b8e7f6753eda1e690e1ff6c92ce27165fa693e