Update from https://crrev.com/317530

tools/clang/blink_gc_plugin/tests/traceimpl.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef TRACEIMPL_H_
 #define TRACEIMPL_H_
 
 #include "heap/stubs.h"
 
 namespace blink {
 
 class X : public GarbageCollected<X> {
  public:
   virtual void trace(Visitor*) {}
 };
 
 class TraceImplInlined : public GarbageCollected<TraceImplInlined> {
  public:
   void trace(Visitor* visitor) { traceImpl(visitor); }
 
   template <typename VisitorDispatcher>
   void traceImpl(VisitorDispatcher visitor) {
-    visitor->trace(m_x);
+    visitor->trace(x_);
   }
 
  private:
-  Member<X> m_x;
+  Member<X> x_;
 };
 
 class TraceImplExtern : public GarbageCollected<TraceImplExtern> {
  public:
   void trace(Visitor* visitor);
   template <typename VisitorDispatcher>
   inline void traceImpl(VisitorDispatcher);
 
  private:
-  Member<X> m_x;
+  Member<X> x_;
 };
+
+class Base : public GarbageCollected<Base> {
+ public:
+  virtual void trace(Visitor* visitor) {}
+};
+
+class TraceImplBaseInlined : public Base {
+ public:
+  void trace(Visitor* visitor) override { traceImpl(visitor); }
+
+  template <typename VisitorDispatcher>
+  void traceImpl(VisitorDispatcher visitor) {
+    Base::trace(visitor);
+  }
+};
+
+class TraceImplBaseExtern : public Base {
+ public:
+  void trace(Visitor* visitor) override;
+
+  template <typename VisitorDispatcher>
+  void traceImpl(VisitorDispatcher);
+
+ private:
+  Member<X> x_;
+};
+
 }
 
 #endif