mac: Several minor fixes to allocator shim.

base/allocator/allocator_shim_override_mac_symbols.h

 // 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.
 
 #ifdef BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_MAC_SYMBOLS_H_
 #error This header is meant to be included only once by allocator_shim.cc
 #endif
 #define BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_MAC_SYMBOLS_H_
 
-#include "base/allocator/allocator_interception_mac.h"
 #include "base/allocator/malloc_zone_functions_mac.h"
 #include "third_party/apple_apsl/malloc.h"
 
 namespace base {
 namespace allocator {
 
-void OverrideMacSymbols() {
+MallocZoneFunctions MallocZoneFunctionsToReplaceDefault() {
   MallocZoneFunctions new_functions;
+  memset(&new_functions, 0, sizeof(MallocZoneFunctions));
   new_functions.size = [](malloc_zone_t* zone, const void* ptr) -> size_t {
     return ShimGetSizeEstimate(ptr, zone);
   };
   new_functions.malloc = [](malloc_zone_t* zone, size_t size) -> void* {
     return ShimMalloc(size, zone);
   };
   new_functions.calloc = [](malloc_zone_t* zone, size_t n,
                             size_t size) -> void* {
     return ShimCalloc(n, size, zone);
   };
@@ skipping 17 matching lines @@
     ShimBatchFree(to_be_freed, num_to_be_freed, zone);
   };
   new_functions.memalign = [](malloc_zone_t* zone, size_t alignment,
                               size_t size) -> void* {
     return ShimMemalign(alignment, size, zone);
   };
   new_functions.free_definite_size = [](malloc_zone_t* zone, void* ptr,
                                         size_t size) {
     ShimFreeDefiniteSize(ptr, size, zone);
   };
-
-  base::allocator::ReplaceFunctionsForStoredZones(&new_functions);
+  return new_functions;
 }
 
 }  // namespace allocator
 }  // namespace base