Move getRecentTasks() to ParceledListSlice.

In extreme cases the list of recent tasks can grow beyond the size
of a single Binder transaction.  This change moves over to
ParceledListSlice which handles chunking any large results.

Bug: 29635557
Change-Id: Iaf1227234f5f8c9451f73a6a5c1dc89f2067f05f
7 files changed