MemorySanitizer support.

runtime/platform/address_sanitizer.h

Index: runtime/platform/address_sanitizer.h
===================================================================
--- runtime/platform/address_sanitizer.h	(revision 0)
+++ runtime/platform/address_sanitizer.h	(working copy)
@@ -0,0 +1,23 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef PLATFORM_ADDRESS_SANITIZER_H_
+#define PLATFORM_ADDRESS_SANITIZER_H_
+
+#include "platform/globals.h"
+
+// Allow the use of ASan (AddressSanitizer). This is needed as ASan needs to be
+// told about areas where the VM does the equivalent of a long-jump.
+#if defined(__has_feature)
+#if __has_feature(address_sanitizer)
+extern "C" void __asan_unpoison_memory_region(void *, size_t);
+#define ASAN_UNPOISON(ptr, len) __asan_unpoison_memory_region(ptr, len)
+#else  // __has_feature(address_sanitizer)
+#define ASAN_UNPOISON(ptr, len) do {} while (false && (ptr) == 0 && (len) == 0)
+#endif  // __has_feature(address_sanitizer)
+#else  // defined(__has_feature)
+#define ASAN_UNPOISON(ptr, len) do {} while (false && (ptr) == 0 && (len) == 0)
+#endif  // defined(__has_feature)
+
+#endif  // PLATFORM_ADDRESS_SANITIZER_H_