CrossThreadCopier: Consider arithmetic and enum types as safe.

third_party/WebKit/Source/platform/CrossThreadCopier.h

 /*
  * Copyright (C) 2009, 2010 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 45 matching lines @@
 template <typename T>
 struct CrossThreadCopierPassThrough {
     STATIC_ONLY(CrossThreadCopierPassThrough);
     typedef T Type;
     static Type copy(const T& parameter)
     {
         return parameter;
     }
 };
 
-template <bool isConvertibleToInteger, bool isThreadSafeRefCounted, bool isGarbageCollected, typename T>
+template <typename T, bool isArithmeticOrEnum, bool isThreadSafeRefCounted, bool isGarbageCollected>
 struct CrossThreadCopierBase;
 
-// Integers get passed through without any changes.
-template <typename T>
-struct CrossThreadCopierBase<true, false, false, T> : public CrossThreadCopierPassThrough<T> {
+// Arithmetic values (integers or floats) and enums can be safely copied.
+template <typename T, bool isThreadSafeRefCounted, bool isGarbageCollected>
+struct CrossThreadCopierBase<T, true, isThreadSafeRefCounted, isGarbageCollected> : public CrossThreadCopierPassThrough<T> {
     STATIC_ONLY(CrossThreadCopierBase);
 };
 
-// Custom copy methods.
-template <typename T>
-struct CrossThreadCopierBase<false, true, false, T> {
+// Custom copy method for ThreadSafeRefCounted.
+template <typename T, bool isGarbageCollected>
+struct CrossThreadCopierBase<T, false, true, isGarbageCollected> {
     STATIC_ONLY(CrossThreadCopierBase);
     typedef typename WTF::RemoveTemplate<T, RefPtr>::Type TypeWithoutRefPtr;
     typedef typename WTF::RemoveTemplate<TypeWithoutRefPtr, PassRefPtr>::Type TypeWithoutPassRefPtr;
     typedef typename std::remove_pointer<TypeWithoutPassRefPtr>::type RefCountedType;
 
     // Verify that only one of the above did a change.
     static_assert((std::is_same<RefPtr<RefCountedType>, T>::value
         || std::is_same<PassRefPtr<RefCountedType>, T>::value
         || std::is_same<RefCountedType*, T>::value),
         "only one type modification should be allowed");
 
     typedef PassRefPtr<RefCountedType> Type;
     static Type copy(const T& refPtr)
     {
         return refPtr;
     }
 };
 
+// A pointer to GarbageCollected.
 template <typename T>
-struct CrossThreadCopierBase<false, false, true, T> {
+struct CrossThreadCopierBase<T, false, false, true> {
     STATIC_ONLY(CrossThreadCopierBase);
     typedef typename std::remove_pointer<T>::type TypeWithoutPointer;
     typedef RawPtr<TypeWithoutPointer> Type;
     static Type copy(const T& ptr)
     {
         return ptr;
     }
 };
 
 template <typename T>
-struct CrossThreadCopier : public CrossThreadCopierBase<std::is_convertible<T, int>::value,
+struct CrossThreadCopier : public CrossThreadCopierBase<
+    T,
+    std::is_arithmetic<T>::value || std::is_enum<T>::value,
     WTF::IsSubclassOfTemplate<typename WTF::RemoveTemplate<T, RefPtr>::Type, ThreadSafeRefCounted>::value
     || WTF::IsSubclassOfTemplate<typename std::remove_pointer<T>::type, ThreadSafeRefCounted>::value
     || WTF::IsSubclassOfTemplate<typename WTF::RemoveTemplate<T, PassRefPtr>::Type, ThreadSafeRefCounted>::value,
-    WTF::IsSubclassOfTemplate<typename std::remove_pointer<T>::type, GarbageCollected>::value,
-    T> {
+    WTF::IsSubclassOfTemplate<typename std::remove_pointer<T>::type, GarbageCollected>::value> {
     STATIC_ONLY(CrossThreadCopier);
 };
 
 // CrossThreadCopier specializations follow.
 
 // nullptr_t can be passed through without any changes.
 template <>
 struct CrossThreadCopier<std::nullptr_t> : public CrossThreadCopierPassThrough<std::nullptr_t> {
     STATIC_ONLY(CrossThreadCopier);
 };
@@ skipping 130 matching lines @@
 
 template <typename T>
 AllowCrossThreadAccessWrapper<const WeakPtr<T>&> AllowCrossThreadAccess(const WeakPtr<T>& value)
 {
     return AllowCrossThreadAccessWrapper<const WeakPtr<T>&>(value);
 }
 
 } // namespace blink
 
 #endif // CrossThreadCopier_h