blink_gc_plugin: retire overloaded traceImpl detection and handling.

tools/clang/blink_gc_plugin/tests/register_weak_members_template.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 REGISTER_WEAK_MEMBERS_TEMPLATE_H_
 #define REGISTER_WEAK_MEMBERS_TEMPLATE_H_
 
 #include "heap/stubs.h"
 
 namespace blink {
 
 class X : public GarbageCollected<X> {
  public:
-  void Trace(Visitor* visitor) { TraceImpl(visitor); }
-  void Trace(InlinedGlobalMarkingVisitor visitor) { TraceImpl(visitor); }
-
- private:
-  template <typename VisitorDispatcher>
-  void TraceImpl(VisitorDispatcher visitor) {}
+  void Trace(Visitor* visitor) {}
 };
 
 class HasUntracedWeakMembers : public GarbageCollected<HasUntracedWeakMembers> {
  public:
-  void Trace(Visitor* visitor) { TraceImpl(visitor); }
-  void Trace(InlinedGlobalMarkingVisitor visitor) { TraceImpl(visitor); }
+  void Trace(Visitor* visitor) {
+    visitor->template RegisterWeakMembers<
+        HasUntracedWeakMembers, &HasUntracedWeakMembers::ClearWeakMembers>(
+        this);
+  }
 
-  // Don't have to be defined for the purpose of this test.
-  void clearWeakMembers(Visitor* visitor);
+  void ClearWeakMembers(Visitor* visitor);
 
  private:
-  template <typename VisitorDispatcher>
-  void TraceImpl(VisitorDispatcher visitor) {
-    visitor->template RegisterWeakMembers<
-        HasUntracedWeakMembers,
-        &HasUntracedWeakMembers::clearWeakMembers>(this);
-  }
-
   WeakMember<X> x_;
 };
 
 }
 
 #endif  // REGISTER_WEAK_MEMBERS_TEMPLATE_H_