blink_gc_plugin: retire overloaded traceImpl detection and handling.

tools/clang/blink_gc_plugin/tests/legacy_naming/heap/stubs.h

Index: tools/clang/blink_gc_plugin/tests/legacy_naming/heap/stubs.h
diff --git a/tools/clang/blink_gc_plugin/tests/legacy_naming/heap/stubs.h b/tools/clang/blink_gc_plugin/tests/legacy_naming/heap/stubs.h
index f8fde065babc844096fe4155a005b82500a393da..2b965df50029ab289138fd25a7458082058c20f5 100644
--- a/tools/clang/blink_gc_plugin/tests/legacy_naming/heap/stubs.h
+++ b/tools/clang/blink_gc_plugin/tests/legacy_naming/heap/stubs.h
@@ -276,26 +276,13 @@ class HeapHashMap : public HashMap<K, V, void, void, void, HeapAllocator> { };
 template<typename T>
 class PersistentHeapVector : public Vector<T, 0, HeapAllocator> { };
 
-template <typename Derived>
-class VisitorHelper {
-public:
-    template<typename T>
-    void trace(const T&);
-};
-
-class Visitor : public VisitorHelper<Visitor> {
-public:
-    template<typename T, void (T::*method)(Visitor*)>
-    void registerWeakMembers(const T* obj);
-};
-
-class InlinedGlobalMarkingVisitor
-    : public VisitorHelper<InlinedGlobalMarkingVisitor> {
-public:
-    InlinedGlobalMarkingVisitor* operator->() { return this; }
+class Visitor {
+ public:
+  template <typename T, void (T::*method)(Visitor*)>
+  void registerWeakMembers(const T* obj);
 
-    template<typename T, void (T::*method)(Visitor*)>
-    void registerWeakMembers(const T* obj);
+  template <typename T>
+  void trace(const T&);
 };
 
 class GarbageCollectedMixin {