Add proguard rule to keep LayoutManager constructors

This CL adds a proguard file to RecyclerView to keep LayoutManager
constructors so that they can be used via XML. Instead of keeping
this specific to RecyclerView manager, I added the generic rule to
cover all such classes.

Bug: 25517678
Change-Id: Ibf32de50991a5d9450ca9216e6b9530ce753f9d6
2 files changed