Separate inflate from render step

Up until now, createSession will always do a first render. With the new
embedded layoutlib we might want to actually call objects from the
inflated view before doing a render or even do it between renders.
This allows to avoid the first initial render unless needed.

This CL also fixes a bug that would only happen when multiple render
calls are issued. When scrolling, use scrollTo since we likely want
absolute positions, not relative.

Change-Id: I4b1d8388d7218a8de33e25cd546fd965fcb07dc7