Reland: Templatize visitor arguments for TraceTrait mark and trace methods.

Source/platform/heap/HeapTest.cpp

 /*
  * 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 40 matching lines @@
     {
         return new IntWrapper(x);
     }
 
     virtual ~IntWrapper()
     {
         ++s_destructorCalls;
     }
 
     static int s_destructorCalls;
-    static void trace(Visitor*) { }
+    void trace(Visitor*) { }
 
     int value() const { return m_x; }
 
     bool operator==(const IntWrapper& other) const { return other.value() == value(); }
 
     unsigned hash() { return IntHash<int>::hash(m_x); }
 
     IntWrapper(int x) : m_x(x) { }
 
 private:
     IntWrapper();
     int m_x;
 };
+static_assert(WTF::NeedsTracing<IntWrapper>::value, "NeedsTracing macro failed to recognize trace method.");
 
 class ThreadMarker {
 public:
     ThreadMarker() : m_creatingThread(reinterpret_cast<ThreadState*>(0)), m_num(0) { }
     ThreadMarker(unsigned i) : m_creatingThread(ThreadState::current()), m_num(i) { }
     ThreadMarker(WTF::HashTableDeletedValueType deleted) : m_creatingThread(reinterpret_cast<ThreadState*>(-1)), m_num(0) { }
     ~ThreadMarker()
     {
         EXPECT_TRUE((m_creatingThread == ThreadState::current())
             || (m_creatingThread == reinterpret_cast<ThreadState*>(0))
@@ skipping 3550 matching lines @@
 
 TEST(HeapTest, CollectionNesting)
 {
     clearOutOldGarbage();
     int* key = &IntWrapper::s_destructorCalls;
     IntWrapper::s_destructorCalls = 0;
     typedef HeapVector<Member<IntWrapper> > IntVector;
     typedef HeapDeque<Member<IntWrapper> > IntDeque;
     HeapHashMap<void*, IntVector>* map = new HeapHashMap<void*, IntVector>();
     HeapHashMap<void*, IntDeque>* map2 = new HeapHashMap<void*, IntDeque>();
+    static_assert(WTF::NeedsTracing<IntVector>::value, "Failed to recognize HeapVector as NeedsTracing");
+    static_assert(WTF::NeedsTracing<IntDeque>::value, "Failed to recognize HeapDeque as NeedsTracing");
 
     map->add(key, IntVector());
     map2->add(key, IntDeque());
 
     HeapHashMap<void*, IntVector>::iterator it = map->find(key);
     EXPECT_EQ(0u, map->get(key).size());
 
     HeapHashMap<void*, IntDeque>::iterator it2 = map2->find(key);
     EXPECT_EQ(0u, map2->get(key).size());
 
@@ skipping 1828 matching lines @@
     // re-adjusting both start&end indices in terms of that expanded buffer.
     EXPECT_EQ(80u, deque->size());
     i = 0;
     for (const auto& intWrapper : *deque) {
         EXPECT_EQ(i + 50, intWrapper->value());
         i++;
     }
 }
 
 } // namespace blink