Various ASan exemptions to allow Oilpan pre-sweep poisoning of unmarkeds.

Source/platform/heap/ThreadState.cpp

Index: Source/platform/heap/ThreadState.cpp
diff --git a/Source/platform/heap/ThreadState.cpp b/Source/platform/heap/ThreadState.cpp
index 699866a4516830374b32646ac8351c86a8c97e33..578e2564ea46b0dd0ffac86edde728d5a3fdf850 100644
--- a/Source/platform/heap/ThreadState.cpp
+++ b/Source/platform/heap/ThreadState.cpp
@@ -898,11 +898,9 @@ void ThreadState::preSweep()
 // TODO(haraken): Currently we cannot enable the poisoning because we have
 // real bugs where destructors touch other on-heap objects. Remove all the bugs
 // and enable the poisoning.
-#if 0
     for (int i = 0; i < NumberOfHeaps; i++)
         m_heaps[i]->poisonUnmarkedObjects();
 #endif
-#endif
 
 #if ENABLE(OILPAN)
     if (gcState() == EagerSweepScheduled) {