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 114 matching lines @@
 //  };
 //
 // The "operator new" for B will enter the forbidden GC scope, but
 // upon construction, two GarbageCollectedMixinConstructorMarker constructors
 // will run -- one for A (first) and another for B (secondly). Only
 // the second one should leave the forbidden GC scope. This is realized by
 // recording the address of B's GarbageCollectedMixinConstructorMarker
 // when the "operator new" for B runs, and leaving the forbidden GC scope
 // when the constructor of the recorded GarbageCollectedMixinConstructorMarker
 // runs.
-#define USING_GARBAGE_COLLECTED_MIXIN(TYPE)                                  \
-  IS_GARBAGE_COLLECTED_TYPE();                                               \
-  DEFINE_GARBAGE_COLLECTED_MIXIN_METHODS(blink::Visitor*, TYPE)              \
-  DEFINE_GARBAGE_COLLECTED_MIXIN_CONSTRUCTOR_MARKER(TYPE)                    \
- public:                                                                     \
-  bool isHeapObjectAlive() const override {                                  \
-    return ThreadHeap::isHeapObjectAlive(this);                              \
-  }                                                                          \
-                                                                             \
+#define USING_GARBAGE_COLLECTED_MIXIN(TYPE)                     \
+  IS_GARBAGE_COLLECTED_TYPE();                                  \
+  DEFINE_GARBAGE_COLLECTED_MIXIN_METHODS(blink::Visitor*, TYPE) \
+  DEFINE_GARBAGE_COLLECTED_MIXIN_CONSTRUCTOR_MARKER(TYPE)       \
+ public:                                                        \
+  bool isHeapObjectAlive() const override {                     \
+    return ThreadHeap::isHeapObjectAlive(this);                 \
+  }                                                             \
+                                                                \
  private:
 
 // An empty class with a constructor that's arranged invoked when all derived
 // constructors of a mixin instance have completed and it is safe to allow GCs
 // again. See AllocateObjectTrait<> comment for more.
 //
 // USING_GARBAGE_COLLECTED_MIXIN() declares a
 // GarbageCollectedMixinConstructorMarker<> private field. By following Blink
 // convention of using the macro at the top of a class declaration, its
 // constructor will run first.
@@ skipping 69 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;
+class WrapperVisitor;
+template <typename T, typename = void>
+struct CanTraceWrappers : std::false_type {};
 
 template <typename T>
-class CanTraceWrappers<T, true> {
-  static_assert(sizeof(T), "T must be fully defined");
-
- 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;
-};
+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