Oilpan: consistently use IsGarbageCollectedMixin<> trait.

Source/platform/heap/Visitor.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 112 matching lines @@
 // By default classes that inherit from GarbageCollectedFinalized need
 // finalization and finalization means calling the 'finalize' method
 // of the object. The FinalizerTrait can be specialized if the default
 // behavior is not desired.
 template<typename T>
 struct FinalizerTrait {
     static const bool nonTrivialFinalizer = WTF::IsSubclassOfTemplate<typename WTF::RemoveConst<T>::Type, GarbageCollectedFinalized>::value;
     static void finalize(void* obj) { FinalizerTraitImpl<T, nonTrivialFinalizer>::finalize(obj); }
 };
 
+// Template to determine if a class is a GarbageCollectedMixin by checking if it
+// has IsGarbageCollectedMixinMarker
+template<typename T>
+struct IsGarbageCollectedMixin {
+private:
+    typedef char YesType;
+    struct NoType {
+        char padding[8];
+    };
+
+    template <typename U> static YesType checkMarker(typename U::IsGarbageCollectedMixinMarker*);
+    template <typename U> static NoType checkMarker(...);
+
+public:
+    static const bool value = sizeof(checkMarker<T>(nullptr)) == sizeof(YesType);
+};
+
 // Trait to get the GCInfo structure for types that have their
 // instances allocated in the Blink garbage-collected heap.
 template<typename T> struct GCInfoTrait;
 
 template<typename T, bool = WTF::IsSubclassOfTemplate<typename WTF::RemoveConst<T>::Type, GarbageCollected>::value> class NeedsAdjustAndMark;
 
 template<typename T>
 class NeedsAdjustAndMark<T, true> {
 public:
     static const bool value = false;
 };
 
 template <typename T> const bool NeedsAdjustAndMark<T, true>::value;
 
 template<typename T>
 class NeedsAdjustAndMark<T, false> {
 public:
-    static const bool value = WTF::IsSubclass<typename WTF::RemoveConst<T>::Type, GarbageCollectedMixin>::value;
+    static const bool value = IsGarbageCollectedMixin<typename WTF::RemoveConst<T>::Type>::value;
 };
 
 template <typename T> const bool NeedsAdjustAndMark<T, false>::value;
 
 template<typename T, bool = NeedsAdjustAndMark<T>::value> class DefaultTraceTrait;
 
 // HasInlinedTraceMethod<T>::value is true for T supporting
 // T::trace(InlinedGlobalMarkingVisitor).
 // The template works by checking if T::HasInlinedTraceMethodMarker type is
 // available using SFINAE. The HasInlinedTraceMethodMarker type is defined
@@ skipping 874 matching lines @@
     USING_GARBAGE_COLLECTED_MIXIN_BASE(TYPE)
 
 #if ENABLE(OILPAN)
 #define WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(TYPE) USING_GARBAGE_COLLECTED_MIXIN(TYPE)
 #define WILL_BE_USING_GARBAGE_COLLECTED_MIXIN_NESTED(TYPE, NESTEDMIXIN) USING_GARBAGE_COLLECTED_MIXIN_NESTED(TYPE, NESTEDMIXIN)
 #else
 #define WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(TYPE)
 #define WILL_BE_USING_GARBAGE_COLLECTED_MIXIN_NESTED(TYPE, NESTEDMIXIN)
 #endif
 
-// Template to determine if a class is a GarbageCollectedMixin by checking if it
-// has IsGarbageCollectedMixinMarker
-template<typename T>
-struct IsGarbageCollectedMixin {
-private:
-    typedef char YesType;
-    struct NoType {
-        char padding[8];
-    };
-
-    template <typename U> static YesType checkMarker(typename U::IsGarbageCollectedMixinMarker*);
-    template <typename U> static NoType checkMarker(...);
-
-public:
-    static const bool value = sizeof(checkMarker<T>(nullptr)) == sizeof(YesType);
-};
-
 // 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.
 template<typename T>
 class GarbageCollectedMixinConstructorMarker {
 public:
@@ skipping 85 matching lines @@
 struct GCInfoTrait {
     static size_t index()
     {
         return GCInfoAtBase<typename GetGarbageCollectedBase<T>::type>::index();
     }
 };
 
 } // namespace blink
 
 #endif // Visitor_h