blink_gc_plugin: retire overloaded traceImpl detection and handling.

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(x_);
-  }
+  void Trace(Visitor* visitor) { visitor->Trace(x_); }
 
  private:
   Member<X> x_;
 };
 
 class TraceImplExtern : public GarbageCollected<TraceImplExtern> {
  public:
   void Trace(Visitor* visitor);
-  template <typename VisitorDispatcher>
-  inline void TraceImpl(VisitorDispatcher);
 
  private:
   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);
-  }
+  void Trace(Visitor* visitor) override { Base::Trace(visitor); }
 };
 
 class TraceImplBaseExtern : public Base {
  public:
   void Trace(Visitor* visitor) override;
 
-  template <typename VisitorDispatcher>
-  void TraceImpl(VisitorDispatcher);
-
  private:
   Member<X> x_;
 };
 
 }
 
 #endif