Hook up allocator shim on mac.

base/allocator/allocator_shim_default_dispatch_to_mac_zoned_malloc.h

Index: base/allocator/allocator_shim_default_dispatch_to_mac_zoned_malloc.h
diff --git a/base/allocator/allocator_shim_default_dispatch_to_mac_zoned_malloc.h b/base/allocator/allocator_shim_default_dispatch_to_mac_zoned_malloc.h
new file mode 100644
index 0000000000000000000000000000000000000000..9e26d826d6fbe32f03860014a69d464821a49b51
--- /dev/null
+++ b/base/allocator/allocator_shim_default_dispatch_to_mac_zoned_malloc.h
@@ -0,0 +1,21 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_ALLOCATOR_SHIM_DEFAULT_DISPATCH_TO_ZONED_MALLOC_H_
+#define BASE_ALLOCATOR_ALLOCATOR_SHIM_DEFAULT_DISPATCH_TO_ZONED_MALLOC_H_
+
+#include "base/allocator/allocator_interception_mac.h"
+
+namespace base {
+namespace allocator {
+
+// This initializes AllocatorDispatch::default_dispatch by saving pointers to
+// the functions in the current default malloc zone. This must be called before
+// the default malloc zone is changed to have its intended effect.
+void InitializeDefaultDispatchToMacAllocator();
+
+}  // namespace allocator
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_ALLOCATOR_SHIM_DEFAULT_DISPATCH_TO_ZONED_MALLOC_H_