Don't zero out memory added to a free list if ASan is enabled

Source/platform/heap/Heap.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 380 matching lines @@
 
 const size_t finalizedHeaderSize = sizeof(FinalizedHeapObjectHeader);
 
 class FreeListEntry : public HeapObjectHeader {
 public:
     NO_SANITIZE_ADDRESS
     explicit FreeListEntry(size_t size)
         : HeapObjectHeader(freeListEncodedSize(size))
         , m_next(0)
     {
-#if !defined(NDEBUG) && !ASAN
+#if !defined(NDEBUG) && !defined(ADDRESS_SANITIZER)
         // Zap free area with asterisks, aka 0x2a2a2a2a.
-        // For ASAN don't zap since we keep accounting in the freelist entry.
+        // For ASan don't zap since we keep accounting in the freelist entry.
         for (size_t i = sizeof(*this); i < size; i++)
             reinterpret_cast<Address>(this)[i] = freelistZapValue;
         ASSERT(size >= objectHeaderSize);
         zapMagic();
 #endif
     }
 
     Address address() { return reinterpret_cast<Address>(this); }
 
     NO_SANITIZE_ADDRESS
@@ skipping 952 matching lines @@
     Address headerAddress = m_currentAllocationPoint;
     m_currentAllocationPoint += allocationSize;
     m_remainingAllocationSize -= allocationSize;
     Header* header = new (NotNull, headerAddress) Header(allocationSize, gcInfo);
     size_t payloadSize = allocationSize - sizeof(Header);
     stats().increaseObjectSpace(payloadSize);
     Address result = headerAddress + sizeof(*header);
     ASSERT(!(reinterpret_cast<uintptr_t>(result) & allocationMask));
     // Unpoison the memory used for the object (payload).
     ASAN_UNPOISON_MEMORY_REGION(result, payloadSize);
-#if !defined(NDEBUG) || defined(LEAK_SANITIZER)
+#if !defined(NDEBUG) || defined(LEAK_SANITIZER) || defined(ADDRESS_SANITIZER)
     memset(result, 0, payloadSize);
 #endif
     ASSERT(heapPageFromAddress(headerAddress + allocationSize - 1));
     return result;
 }
 
 // FIXME: Allocate objects that do not need finalization separately
 // and use separate sweeping to not have to check for finalizers.
 template<typename T>
 Address Heap::allocate(size_t size)
@@ skipping 960 matching lines @@
 };
 
 template<typename T>
 struct IfWeakMember<WeakMember<T> > {
     static bool isDead(Visitor* visitor, const WeakMember<T>& t) { return !visitor->isAlive(t.get()); }
 };
 
 }
 
 #endif // Heap_h