Revert "Support ES6 Map and Set in heap profiler"

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 329570f0e55c2e4305011e2a26a847149d319117..e18d70a22032d6b69c7aa49596bc270f339283cb 100644
--- a/src/heap-snapshot-generator.h
+++ b/src/heap-snapshot-generator.h
@@ -370,7 +370,6 @@ class V8HeapExplorer : public HeapEntriesAllocator {
   void ExtractJSObjectReferences(int entry, JSObject* js_obj);
   void ExtractStringReferences(int entry, String* obj);
   void ExtractSymbolReferences(int entry, Symbol* symbol);
-  void ExtractJSCollectionReferences(int entry, JSCollection* collection);
   void ExtractJSWeakCollectionReferences(int entry,
                                          JSWeakCollection* collection);
   void ExtractContextReferences(int entry, Context* context);