Hook up allocator shim on mac.

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..c90b4c8e879d8fe689fbdc1087e2182ec64c68ba 100644
--- a/base/allocator/allocator_shim_default_dispatch_to_tcmalloc.cc
+++ b/base/allocator/allocator_shim_default_dispatch_to_tcmalloc.cc
@@ -44,6 +44,9 @@ 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,            /* free_definite_size_function */
     nullptr,            /* next */
 };