Cleaned up the weak lists hanging off the heap a bit.

src/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_H_
 #define V8_HEAP_H_
 
 #include <cmath>
 
 #include "allocation.h"
@@ skipping 815 matching lines @@
   INTERNALIZED_STRING_LIST(STRING_ACCESSOR)
 #undef STRING_ACCESSOR
 
   // The hidden_string is special because it is the empty string, but does
   // not match the empty string.
   String* hidden_string() { return hidden_string_; }
 
   void set_native_contexts_list(Object* object) {
     native_contexts_list_ = object;
   }
-  Object* native_contexts_list() { return native_contexts_list_; }
+  Object* native_contexts_list() const { return native_contexts_list_; }
 
   void set_array_buffers_list(Object* object) {
     array_buffers_list_ = object;
   }
-  Object* array_buffers_list() { return array_buffers_list_; }
+  Object* array_buffers_list() const { return array_buffers_list_; }
 
   void set_allocation_sites_list(Object* object) {
     allocation_sites_list_ = object;
   }
   Object* allocation_sites_list() { return allocation_sites_list_; }
+
+  // Used in CreateAllocationSiteStub and the (de)serializer.
   Object** allocation_sites_list_address() { return &allocation_sites_list_; }
 
   Object* weak_object_to_code_table() { return weak_object_to_code_table_; }
 
   // Number of mark-sweeps.
   unsigned int ms_count() { return ms_count_; }
 
   // Iterates over all roots in the heap.
   void IterateRoots(ObjectVisitor* v, VisitMode mode);
   // Iterates over all strong roots in the heap.
@@ skipping 72 matching lines @@
     roots_[kMaterializedObjectsRootIndex] = objects;
   }
 
   // Generated code can embed this address to get access to the roots.
   Object** roots_array_start() { return roots_; }
 
   Address* store_buffer_top_address() {
     return reinterpret_cast<Address*>(&roots_[kStoreBufferTopRootIndex]);
   }
 
-  // Get address of native contexts list for serialization support.
-  Object** native_contexts_list_address() {
-    return &native_contexts_list_;
-  }
-
 #ifdef VERIFY_HEAP
   // Verify the heap is in its normal state before or after a GC.
   void Verify();
 
 
   bool weak_embedded_objects_verification_enabled() {
     return no_weak_object_verification_scope_depth_ == 0;
   }
 #endif
 
@@ skipping 1867 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_