Allow arbitrary names for weak references in heap snapshots.

src/heap-snapshot-generator.h

 // Copyright 2013 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 39 matching lines @@
     kWeak = v8::HeapGraphEdge::kWeak
   };
 
   HeapGraphEdge() { }
   HeapGraphEdge(Type type, const char* name, int from, int to);
   HeapGraphEdge(Type type, int index, int from, int to);
   void ReplaceToIndexWithEntry(HeapSnapshot* snapshot);
 
   Type type() const { return static_cast<Type>(type_); }
   int index() const {
-    ASSERT(type_ == kElement || type_ == kHidden || type_ == kWeak);
+    ASSERT(type_ == kElement || type_ == kHidden);
     return index_;
   }
   const char* name() const {
     ASSERT(type_ == kContextVariable
         || type_ == kProperty
         || type_ == kInternal
-        || type_ == kShortcut);
+        || type_ == kShortcut
+        || type_ == kWeak);
     return name_;
   }
   INLINE(HeapEntry* from() const);
   HeapEntry* to() const { return to_entry_; }
 
  private:
   INLINE(HeapSnapshot* snapshot() const);
 
   unsigned type_ : 3;
   int from_index_ : 29;
@@ skipping 363 matching lines @@
                             int parent,
                             int index,
                             Object* child,
                             int field_offset = -1);
   void SetHiddenReference(HeapObject* parent_obj,
                           int parent,
                           int index,
                           Object* child);
   void SetWeakReference(HeapObject* parent_obj,
                         int parent,
-                        int index,
+                        const char* reference_name,
                         Object* child_obj,
                         int field_offset);
   void SetPropertyReference(HeapObject* parent_obj,
                             int parent,
                             Name* reference_name,
                             Object* child,
                             const char* name_format_string = NULL,
                             int field_offset = -1);
   void SetUserGlobalReference(Object* user_global);
   void SetRootGcRootsReference();
@@ skipping 172 matching lines @@
   friend class HeapSnapshotJSONSerializerEnumerator;
   friend class HeapSnapshotJSONSerializerIterator;
 
   DISALLOW_COPY_AND_ASSIGN(HeapSnapshotJSONSerializer);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_SNAPSHOT_GENERATOR_H_