Update from https://crrev.com/318214

tools/clang/blink_gc_plugin/tests/trace_after_dispatch_impl.h

+// Copyright 2015 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 TRACE_AFTER_DISPATCH_IMPL_H_
+#define TRACE_AFTER_DISPATCH_IMPL_H_
+
+#include "heap/stubs.h"
+
+namespace blink {
+
+class X : public GarbageCollected<X> {
+ public:
+  void trace(Visitor*) {}
+};
+
+enum ClassTag {
+  BASE, DERIVED
+};
+
+class TraceAfterDispatchInlinedBase
+    : public GarbageCollected<TraceAfterDispatchInlinedBase> {
+ public:
+  explicit TraceAfterDispatchInlinedBase(ClassTag tag) : tag_(tag) {}
+
+  void trace(Visitor* visitor);
+
+  void traceAfterDispatch(Visitor* visitor) { traceAfterDispatchImpl(visitor); }
+
+ private:
+  template <typename VisitorDispatcher>
+  void traceAfterDispatchImpl(VisitorDispatcher visitor) {
+    visitor->trace(x_base_);
+  }
+
+  ClassTag tag_;
+  Member<X> x_base_;
+};
+
+class TraceAfterDispatchInlinedDerived : public TraceAfterDispatchInlinedBase {
+ public:
+  TraceAfterDispatchInlinedDerived() : TraceAfterDispatchInlinedBase(DERIVED) {}
+
+  void traceAfterDispatch(Visitor* visitor) { traceAfterDispatchImpl(visitor); }
+
+ private:
+  template <typename VisitorDispatcher>
+  void traceAfterDispatchImpl(VisitorDispatcher visitor) {
+    visitor->trace(x_derived_);
+    TraceAfterDispatchInlinedBase::traceAfterDispatch(visitor);
+  }
+
+  Member<X> x_derived_;
+};
+
+class TraceAfterDispatchExternBase
+    : public GarbageCollected<TraceAfterDispatchExternBase> {
+ public:
+  explicit TraceAfterDispatchExternBase(ClassTag tag) : tag_(tag) {}
+
+  void trace(Visitor* visitor);
+
+  void traceAfterDispatch(Visitor* visitor);
+
+ private:
+  template <typename VisitorDispatcher>
+  void traceAfterDispatchImpl(VisitorDispatcher visitor);
+
+  ClassTag tag_;
+  Member<X> x_base_;
+};
+
+class TraceAfterDispatchExternDerived : public TraceAfterDispatchExternBase {
+ public:
+  TraceAfterDispatchExternDerived() : TraceAfterDispatchExternBase(DERIVED) {}
+
+  void traceAfterDispatch(Visitor* visitor);
+
+ private:
+  template <typename VisitorDispatcher>
+  void traceAfterDispatchImpl(VisitorDispatcher visitor);
+
+  Member<X> x_derived_;
+};
+
+}
+
+#endif  // TRACE_AFTER_DISPATCH_IMPL_H_