Add RecordFree to the GarbageCollector interface

RecordFree now calls the Heap::RecordFree as well as updates the
garbage collector's internal bytes freed accounting.

Change-Id: I8cb03748b0768e3c8c50ea709572960e6e4ad219
diff --git a/runtime/gc/heap.h b/runtime/gc/heap.h
index 7eafd34..7a9ef1e 100644
--- a/runtime/gc/heap.h
+++ b/runtime/gc/heap.h
@@ -358,7 +358,7 @@
 
   // Freed bytes can be negative in cases where we copy objects from a compacted space to a
   // free-list backed space.
-  void RecordFree(ssize_t freed_objects, ssize_t freed_bytes);
+  void RecordFree(uint64_t freed_objects, int64_t freed_bytes);
 
   // Must be called if a field of an Object in the heap changes, and before any GC safe-point.
   // The call is not needed if NULL is stored in the field.