[heap] Get rid of dead code in HeapIterator.

src/heap/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 2561 matching lines @@
 //
 // 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 HeapIterator BASE_EMBEDDED {
  public:
   enum HeapObjectsFiltering { kNoFiltering, kFilterUnreachable };
 
-  explicit HeapIterator(Heap* heap);
-  HeapIterator(Heap* heap, HeapObjectsFiltering filtering);
+  explicit HeapIterator(Heap* heap,
+                        HeapObjectsFiltering filtering = kNoFiltering);
   ~HeapIterator();
 
   HeapObject* next();
-  void reset();
 
  private:
   struct MakeHeapIterableHelper {
     explicit MakeHeapIterableHelper(Heap* heap) { heap->MakeHeapIterable(); }
   };
 
-  // Perform the initialization.
-  void Init();
-  // Perform all necessary shutdown (destruction) work.
-  void Shutdown();
   HeapObject* NextObject();
 
+  // The following two fields need to be declared in this order. Initialization
+  // order guarantees that we first make the heap iterable (which may involve
+  // allocations) and only then lock it down by not allowing further
+  // allocations.
   MakeHeapIterableHelper make_heap_iterable_helper_;
   DisallowHeapAllocation no_heap_allocation_;
+
   Heap* heap_;
   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_;
 };
 
 
@@ skipping 175 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_HEAP_H_