Change cast to String to cast to Symbol in heap-snapshot-generator.

src/heap-snapshot-generator.cc

Index: src/heap-snapshot-generator.cc
diff --git a/src/heap-snapshot-generator.cc b/src/heap-snapshot-generator.cc
index 13f40db799be1f6332e412fbfc90ee5f77313156..68522fccec653dc9c67fda812cfab11ec76b6d7c 100644
--- a/src/heap-snapshot-generator.cc
+++ b/src/heap-snapshot-generator.cc
@@ -1698,7 +1698,7 @@ void V8HeapExplorer::ExtractPropertyReferences(JSObject* js_obj, int entry) {
           continue;
         }
         if (ExtractAccessorPairProperty(js_obj, entry, k, value)) continue;
-        SetPropertyReference(js_obj, entry, String::cast(k), value);
+        SetPropertyReference(js_obj, entry, Name::cast(k), value);
       }
     }
   }