[wrapper-tracing] Redesign dispatching on non-inheriting cases

third_party/WebKit/Source/platform/heap/GarbageCollected.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 GarbageCollected_h
 #define GarbageCollected_h
 
 #include "platform/heap/ThreadState.h"
 #include "wtf/Allocator.h"
 #include "wtf/Assertions.h"
@@ skipping 228 matching lines @@
 
 template <typename T>
 class NeedsAdjustAndMark<T, false> {
   static_assert(sizeof(T), "T must be fully defined");
 
  public:
   static const bool value =
       IsGarbageCollectedMixin<typename std::remove_const<T>::type>::value;
 };
 
-class WrapperVisitor;
-template <typename T, typename = void>
-struct CanTraceWrappers : std::false_type {};
-
-template <typename T>
-struct CanTraceWrappers<T,
-                        decltype(
-                            std::declval<T&>().markAndDispatchTraceWrappers(
-                                std::declval<WrapperVisitor*>()))>
-    : std::true_type {};
-
 // TODO(sof): migrate to wtf/TypeTraits.h
 template <typename T>
 class IsFullyDefined {
   using TrueType = char;
   struct FalseType {
     char dummy[2];
   };
 
   template <typename U, size_t sz = sizeof(U)>
   static TrueType isSizeofKnown(U*);
   static FalseType isSizeofKnown(...);
   static T& t;
 
  public:
   static const bool value = sizeof(TrueType) == sizeof(isSizeofKnown(&t));
 };
 
 }  // namespace blink
 
 #endif