Hook up allocator shim on mac.

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index 69dfcc5b3bbe28700b259a9ad2e2decec8e70b4c..b738521c6aadff8f6a5e520306ce465d279ef3df 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -1144,6 +1144,12 @@ component("base") {
         "allocator/allocator_shim_override_linker_wrapped_symbols.h",
       ]
       all_dependent_configs += [ "//base/allocator:wrap_malloc_symbols" ]
+    } else if (is_mac) {
+      sources += [
+        "allocator/allocator_shim_default_dispatch_to_mac_zoned_malloc.cc",
+        "allocator/allocator_shim_default_dispatch_to_mac_zoned_malloc.h",
+        "allocator/allocator_shim_override_mac_symbols.h",
+      ]
     }
   }