Add methods to animate expansion to the expanded view controller

- Adds the "collapse position" to the collapse methods as the view
  will eventually animate to that point
- Adds new methods to animate the expansion (unused)
- Adds a method to check if the controller should actually animate
  the expansion (returns false)

Test: treehugger
Bug: 311450609
Change-Id: I3d8059a4dffe835cf903552ea8986b488f451540