Expose API for using SurfaceControl with ViewRootImpl

This API is appropriately called "ViewRoot". So far we just expose
an API surface to reparent SurfaceControl to the ViewRoot (but without
exposing the ViewRoot's SurfaceControl, to encourage developers not
to shoot themselves in the foot) and to synchronize with the drawing
of the ViewRoot SurfaceControl.

Bug: 173463039
Test: ViewRootSyncTests
Change-Id: I8ce0ed4b3efe50cdb3b71ae0f05ce25438d42368
6 files changed