Use new ASAN APIs for scanning ASAN fake stacks during garbage collection.

Source/platform/heap/Heap.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 665 matching lines @@
 template<typename Header>
 void ThreadHeap<Header>::getScannedStats(HeapStats& scannedStats)
 {
     for (HeapPage<Header>* page = m_firstPage; page; page = page->next())
         page->getStats(scannedStats);
     for (LargeHeapObject<Header>* current = m_firstLargeHeapObject; current; current = current->next())
         current->getStats(scannedStats);
 }
 #endif
 
+// STRICT_ASAN_FINALIZATION_CHECKING turns on poisoning of all objects during
+// sweeping to catch cases where dead objects touch eachother. This is not
+// turned on by default because it also triggers for cases that are safe.
+// Examples of such safe cases are context life cycle observers and timers
+// embedded in garbage collected objects.
+#define STRICT_ASAN_FINALIZATION_CHECKING 0
+
 template<typename Header>
 void ThreadHeap<Header>::sweep()
 {
     ASSERT(isConsistentForGC());
-#if defined(ADDRESS_SANITIZER)
+#if defined(ADDRESS_SANITIZER) && STRICT_ASAN_FINALIZATION_CHECKING
     // When using ASAN do a pre-sweep where all unmarked objects are poisoned before
     // calling their finalizer methods. This can catch the cases where one objects
     // finalizer tries to modify another object as part of finalization.
     for (HeapPage<Header>* page = m_firstPage; page; page = page->next())
         page->poisonUnmarkedObjects();
 #endif
     HeapPage<Header>* page = m_firstPage;
     HeapPage<Header>** previous = &m_firstPage;
     bool pagesRemoved = false;
     while (page) {
@@ skipping 675 matching lines @@
 // Force template instantiations for the types that we need.
 template class HeapPage<FinalizedHeapObjectHeader>;
 template class HeapPage<HeapObjectHeader>;
 template class ThreadHeap<FinalizedHeapObjectHeader>;
 template class ThreadHeap<HeapObjectHeader>;
 
 Visitor* Heap::s_markingVisitor;
 CallbackStack* Heap::s_markingStack;
 CallbackStack* Heap::s_weakCallbackStack;
 }