Remove WRAPPER_VISITOR_SPECIAL_CLASSES

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"
 #include "wtf/TypeTraits.h"
 
 namespace blink {
 
 template <typename T>
 class GarbageCollected;
-class TraceWrapperBase;
 
 // GC_PLUGIN_IGNORE is used to make the plugin ignore a particular class or
 // field when checking for proper usage.  When using GC_PLUGIN_IGNORE
 // a bug-number should be provided as an argument where the bug describes
 // what needs to happen to remove the GC_PLUGIN_IGNORE again.
 #if COMPILER(CLANG)
 #define GC_PLUGIN_IGNORE(bug) \
   __attribute__((annotate("blink_gc_plugin_ignore")))
 #else
 #define GC_PLUGIN_IGNORE(bug)
@@ skipping 212 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;
 };
 
-template <typename T,
-          bool = std::is_base_of<TraceWrapperBase,
-                                 typename std::remove_const<T>::type>::value>
-class CanTraceWrappers;
+template <typename T>
+class CanTraceWrappers {

[adithyas, 2017/03/03 21:40:07]

I don't know if this is useful anymore, I think the compiler would warn that "T"
does not have markAndDispatchTraceWrappers defined regardless.

[Michael Lippautz, 2017/03/07 08:00:00]

I would keep it as we should be able to generate better error messages using
this one.

+  typedef char YesType;
+  typedef long NoType;
 
-template <typename T>
-class CanTraceWrappers<T, true> {
-  static_assert(sizeof(T), "T must be fully defined");
+  template <typename U>
+  static YesType TypeHasMarkAndDispatchTraceWrappers(
+      decltype(&U::markAndDispatchTraceWrappers) *);
+  template <typename U>
+  static NoType TypeHasMarkAndDispatchTraceWrappers(...);
 
  public:
-  static const bool value = true;
-};
-
-template <typename T>
-class CanTraceWrappers<T, false> {
-  static_assert(sizeof(T), "T must be fully defined");
-
- public:
-  static const bool value = false;
+  static bool const value =
+      (sizeof(TypeHasMarkAndDispatchTraceWrappers<T>(0)) == sizeof(YesType));
 };
 
 // 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