Fix ThreadHeap::isHeapObjectAlive(const T*& ptr) stack overflow.

third_party/WebKit/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 724 matching lines @@
 
   int m_traceCount;
 };
 
 class ClassWithMember : public GarbageCollected<ClassWithMember> {
  public:
   static ClassWithMember* create() { return new ClassWithMember(); }
 
   DEFINE_INLINE_TRACE() {
     EXPECT_TRUE(ThreadHeap::isHeapObjectAlive(this));
+
+    // Const pointer should also be alive. See http://crbug.com/661363.
+    const ClassWithMember* constPtr = static_cast<const ClassWithMember*>(this);
+    EXPECT_TRUE(ThreadHeap::isHeapObjectAlive(constPtr));
+
     if (!traceCount())
       EXPECT_FALSE(ThreadHeap::isHeapObjectAlive(m_traceCounter));
     else
       EXPECT_TRUE(ThreadHeap::isHeapObjectAlive(m_traceCounter));
 
     visitor->trace(m_traceCounter);
   }
 
   int traceCount() { return m_traceCounter->traceCount(); }
 
@@ skipping 6046 matching lines @@
       "HeapVector");
   static_assert(
       WTF::IsGarbageCollectedType<HeapDeque<Member<IntWrapper>>>::value,
       "HeapDeque");
   static_assert(WTF::IsGarbageCollectedType<
                     HeapTerminatedArray<Member<IntWrapper>>>::value,
                 "HeapTerminatedArray");
 }
 
 }  // namespace blink