Implement HeapIterator that skips over unreachable objects.

src/heap.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1567 matching lines @@
 
 // A HeapIterator provides iteration over the whole heap. It
 // aggregates the specific iterators for the different spaces as
 // these can only iterate over one space only.
 //
 // HeapIterator can skip free list nodes (that is, de-allocated heap
 // objects that still remain in the heap). As implementation of free
 // nodes filtering uses GC marks, it can't be used during MS/MC GC
 // phases. Also, it is forbidden to interrupt iteration in this mode,
 // as this will leave heap objects marked (and thus, unusable).
-class FreeListNodesFilter;
+class HeapObjectsFilter;
 
 class HeapIterator BASE_EMBEDDED {
  public:
-  enum FreeListNodesFiltering {
+  enum HeapObjectsFiltering {
     kNoFiltering,
-    kPreciseFiltering
+    kFilterFreeListNodes,
+    kFilterUnreachable
   };
 
   HeapIterator();
-  explicit HeapIterator(FreeListNodesFiltering filtering);
+  explicit HeapIterator(HeapObjectsFiltering filtering);
   ~HeapIterator();
 
   HeapObject* next();
   void reset();
 
  private:
   // Perform the initialization.
   void Init();
   // Perform all necessary shutdown (destruction) work.
   void Shutdown();
   HeapObject* NextObject();
 
-  FreeListNodesFiltering filtering_;
-  FreeListNodesFilter* filter_;
+  HeapObjectsFiltering filtering_;
+  HeapObjectsFilter* filter_;
   // Space iterator for iterating all the spaces.
   SpaceIterator* space_iterator_;
   // Object iterator for the space currently being iterated.
   ObjectIterator* object_iterator_;
 };
 
 
 // Cache for mapping (map, property name) into field offset.
 // Cleared at startup and prior to mark sweep collection.
 class KeyedLookupCache {
@@ skipping 483 matching lines @@
   // Return whether this object should be retained. If NULL is returned the
   // object has no references. Otherwise the address of the retained object
   // should be returned as in some GC situations the object has been moved.
   virtual Object* RetainAs(Object* object) = 0;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_