Hook up allocator shim on mac.

base/allocator/allocator_shim_default_dispatch_to_glibc.cc

 // Copyright 2016 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.
 
 #include "base/allocator/allocator_shim.h"
 
 #include <malloc.h>
 
 // This translation unit defines a default dispatch for the allocator shim which
 // routes allocations to libc functions.
@@ skipping 39 matching lines @@
 
 }  // namespace
 
 const AllocatorDispatch AllocatorDispatch::default_dispatch = {
     &GlibcMalloc,          /* alloc_function */
     &GlibcCalloc,          /* alloc_zero_initialized_function */
     &GlibcMemalign,        /* alloc_aligned_function */
     &GlibcRealloc,         /* realloc_function */
     &GlibcFree,            /* free_function */
     &GlibcGetSizeEstimate, /* get_size_estimate_function */
+    nullptr,               /* batch_malloc_function */
+    nullptr,               /* batch_free_function */
+    nullptr,               /* free_definite_size_function */
     nullptr,               /* next */
 };