Remove WRAPPER_VISITOR_SPECIAL_CLASSES

third_party/WebKit/Source/platform/heap/GarbageCollected.h

Index: third_party/WebKit/Source/platform/heap/GarbageCollected.h
diff --git a/third_party/WebKit/Source/platform/heap/GarbageCollected.h b/third_party/WebKit/Source/platform/heap/GarbageCollected.h
index eb6c3166de979c5cbe027b516b2758ab1b0d8096..c05abff58da025f331a6613547eaa912b0fa8ca5 100644
--- a/third_party/WebKit/Source/platform/heap/GarbageCollected.h
+++ b/third_party/WebKit/Source/platform/heap/GarbageCollected.h
@@ -14,7 +14,6 @@ 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
@@ -247,25 +246,20 @@ class NeedsAdjustAndMark<T, false> {
       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<T, true> {
-  static_assert(sizeof(T), "T must be fully defined");
-
- public:
-  static const bool value = true;
-};
+class CanTraceWrappers {

[jbroman, 2017/03/07 17:46:09]

nit: Slightly more concisely (and happens to also check that it's a function
that returns void, not that it matters much):

template <typename T, typename = void>
struct CanTraceWrappers : std::false_type {};

template <typename T>
struct HasFoo<T, decltype(std::declval<T&>().markAndDispatchTraceWrappers())> :
std::true_type {};

[jbroman, 2017/03/07 17:47:38]

Err, replace "HasFoo" with "CanTraceWrappers". Forgot to replace that when
editing.

[adithyas, 2017/03/07 18:40:46]

Much better, thanks!

+  typedef char YesType;
+  typedef long NoType;
 
-template <typename T>
-class CanTraceWrappers<T, false> {
-  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 = false;
+  static bool const value =

[jbroman, 2017/03/07 17:46:09]

nit: If you do keep this, prefer "const bool" to "bool const".

+      (sizeof(TypeHasMarkAndDispatchTraceWrappers<T>(0)) == sizeof(YesType));
 };
 
 // TODO(sof): migrate to wtf/TypeTraits.h