Reuse fileList and more from PatchSreen when switching types

Reuse many of the PatchScreen details when switching from
Side-By-Side to Unified and vice versa.  This can save a lot
of time and CPU when fileLists are large and at least one RPC.

Change-Id: Ibcc58f9c3bac3ebef0b8dc2250d9e0bd1e003b15