Allow arbitrary names for weak references in heap snapshots.

src/heap-snapshot-generator.h

Index: src/heap-snapshot-generator.h
diff --git a/src/heap-snapshot-generator.h b/src/heap-snapshot-generator.h
index d93362f63bc1a6d61fa90792b660a1e0b9432a2a..59d324e499cf8daeabc404a6f05f501a28397d0e 100644
--- a/src/heap-snapshot-generator.h
+++ b/src/heap-snapshot-generator.h
@@ -57,14 +57,15 @@ class HeapGraphEdge BASE_EMBEDDED {
 
   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);
@@ -448,7 +449,7 @@ class V8HeapExplorer : public HeapEntriesAllocator {
                           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,