Add a generic remembered set class.

src/heap/spaces.h

Index: src/heap/spaces.h
diff --git a/src/heap/spaces.h b/src/heap/spaces.h
index 3674551a13bc9310ede67754bd715b20d8f320a3..10c351ec662b95c054ef7379a4451c976e73c55e 100644
--- a/src/heap/spaces.h
+++ b/src/heap/spaces.h
@@ -398,6 +398,7 @@ class MemoryChunk {
   static const size_t kWriteBarrierCounterOffset =
       kSlotsBufferOffset + kPointerSize  // SlotsBuffer* slots_buffer_;
       + kPointerSize                     // SlotSet* old_to_new_slots_;
+      + kPointerSize                     // SlotSet* old_to_old_slots_;
       + kPointerSize;                    // SkipList* skip_list_;
 
   static const size_t kMinHeaderSize =
@@ -445,7 +446,7 @@ class MemoryChunk {
     MemoryChunk::FromAddress(object->address())->IncrementLiveBytes(by);
   }
 
-  // Only works for addresses in pointer spaces, not data or code spaces.
+  // Only works for addresses in pointer spaces, not code space.
   static inline MemoryChunk* FromAnyPointerAddress(Heap* heap, Address addr);
 
   static inline uint32_t FastAddressToMarkbitIndex(Address addr) {
@@ -678,8 +679,12 @@ class MemoryChunk {
 
   inline SlotSet* old_to_new_slots() { return old_to_new_slots_; }
 
+  inline SlotSet* old_to_old_slots() { return old_to_old_slots_; }
+
   void AllocateOldToNewSlots();
   void ReleaseOldToNewSlots();
+  void AllocateOldToOldSlots();
+  void ReleaseOldToOldSlots();
 
   void MarkEvacuationCandidate() {
     DCHECK(!IsFlagSet(NEVER_EVACUATE));
@@ -732,6 +737,7 @@ class MemoryChunk {
   // set for large pages. In the latter case the number of entries in the array
   // is ceil(size() / kPageSize).
   SlotSet* old_to_new_slots_;
+  SlotSet* old_to_old_slots_;
   SkipList* skip_list_;
   intptr_t write_barrier_counter_;
   // Assuming the initial allocation on a page is sequential,
@@ -781,6 +787,9 @@ class Page : public MemoryChunk {
     return reinterpret_cast<Page*>(OffsetFrom(a) & ~kPageAlignmentMask);
   }
 
+  // Only works for addresses in pointer spaces, not code space.
+  inline static Page* FromAnyPointerAddress(Heap* heap, Address addr);
+
   // Returns the page containing an allocation top. Because an allocation
   // top address can be the upper bound of the page, we need to subtract
   // it with kPointerSize first. The address ranges from