Fix RecordFree to take signed parameters.

RecordFree can get negative bytes allocated when background
compaction foreground transitions occur. This caused a DCHECK to
fail on debug builds. Also did some refactoring in
PreProcessReferences.

Bug: 13568814
Change-Id: I57543f1c78544a94f1d241459698b736dba8cfa8
diff --git a/runtime/gc/collector/mark_sweep.h b/runtime/gc/collector/mark_sweep.h
index b117b20..65583d9 100644
--- a/runtime/gc/collector/mark_sweep.h
+++ b/runtime/gc/collector/mark_sweep.h
@@ -126,7 +126,7 @@
   void ProcessReferences(Thread* self)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
-  void PreProcessReferences(Thread* self)
+  void PreProcessReferences()
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);