mac: Hook up allocator shim.

base/allocator/allocator_shim_default_dispatch_to_tcmalloc.cc

Index: base/allocator/allocator_shim_default_dispatch_to_tcmalloc.cc
diff --git a/base/allocator/allocator_shim_default_dispatch_to_tcmalloc.cc b/base/allocator/allocator_shim_default_dispatch_to_tcmalloc.cc
index 7853422726468ac24eef05f55da667115f2d4fc0..ce0110dc762018e8fa25966e992b701d5a07ca83 100644
--- a/base/allocator/allocator_shim_default_dispatch_to_tcmalloc.cc
+++ b/base/allocator/allocator_shim_default_dispatch_to_tcmalloc.cc
@@ -44,6 +44,8 @@ const AllocatorDispatch AllocatorDispatch::default_dispatch = {
     &TCRealloc,         /* realloc_function */
     &TCFree,            /* free_function */
     &TCGetSizeEstimate, /* get_size_estimate_function */
+    nullptr,            /* batch_malloc_function */
+    nullptr,            /* batch_free_function */
     nullptr,            /* next */
 };