[heap] Move slot filtering logic into sweeper.

src/heap/remembered-set.h

Index: src/heap/remembered-set.h
diff --git a/src/heap/remembered-set.h b/src/heap/remembered-set.h
index d9770025e37195c0cc1aab007a87ddf19550707d..a625b13dbf1fe0deced0b60291c2e86f16b0d0fb 100644
--- a/src/heap/remembered-set.h
+++ b/src/heap/remembered-set.h
@@ -202,13 +202,8 @@ class RememberedSet {
   // slots that are not part of live objects anymore. This method must be
   // called after marking, when the whole transitive closure is known and
   // must be called before sweeping when mark bits are still intact.
-  static void ClearInvalidSlots(Heap* heap);
-
-  static void ClearInvalidSlots(Heap* heap, MemoryChunk* chunk);
   static void ClearInvalidTypedSlots(Heap* heap, MemoryChunk* chunk);
 
-  static void VerifyValidSlots(Heap* heap);
-
  private:
   static SlotSet* GetSlotSet(MemoryChunk* chunk) {
     if (direction == OLD_TO_OLD) {