Oilpan: Fix ASan instrumentation around heap object headers.

Source/platform/heap/Heap.h

Index: Source/platform/heap/Heap.h
diff --git a/Source/platform/heap/Heap.h b/Source/platform/heap/Heap.h
index 07312d258e0f0ac6630af91ec587a49e7b3063b3..05e20f6ecb3cd3bf8757d002345dc8b1801a1fbf 100644
--- a/Source/platform/heap/Heap.h
+++ b/Source/platform/heap/Heap.h
@@ -1497,6 +1497,7 @@ Address HeapObjectHeader::payloadEnd()
     return reinterpret_cast<Address>(this) + size();
 }
 
+NO_SANITIZE_ADDRESS
 void HeapObjectHeader::mark()
 {
     checkHeader();
@@ -1505,12 +1506,13 @@ void HeapObjectHeader::mark()
     // Multiple threads can still read the old value and all store the
     // new value. However, the new value will be the same for all of
     // the threads and the end result is therefore consistent.
-    // We need to unpoison/poison the header on ASAN since
-    // acquireLoad/releaseStore don't have the NO_SANITIZE_ADDRESS flag.
-    ASAN_UNPOISON_MEMORY_REGION(this, sizeof(this));
+#if defined(ADDRESS_SANITIZER)

[zerny-chromium, 2014/09/09 06:01:28]

I'd prefer to avoid the code duplication by defining the asan variants for both
true and false values of defined(ADDRESS_SANITIZER).

[Mads Ager (chromium), 2014/09/09 08:22:14]

Done.

+    unsigned size = asanAcquireLoad(&m_size);
+    asanReleaseStore(&m_size, size | markBitMask);
+#else
     unsigned size = acquireLoad(&m_size);
     releaseStore(&m_size, size | markBitMask);
-    ASAN_POISON_MEMORY_REGION(this, sizeof(this));
+#endif
 }
 
 Address FinalizedHeapObjectHeader::payload()