mac: Several minor fixes to allocator shim.

base/allocator/allocator_shim_override_mac_symbols.h

Index: base/allocator/allocator_shim_override_mac_symbols.h
diff --git a/base/allocator/allocator_shim_override_mac_symbols.h b/base/allocator/allocator_shim_override_mac_symbols.h
index dceba48f6358582383e303fe81ab7b4629c39002..0b65edb154747e8dd0f5440fc434a23f36afa58c 100644
--- a/base/allocator/allocator_shim_override_mac_symbols.h
+++ b/base/allocator/allocator_shim_override_mac_symbols.h
@@ -7,15 +7,15 @@
 #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);
   };
@@ -53,8 +53,7 @@ void OverrideMacSymbols() {
                                         size_t size) {
     ShimFreeDefiniteSize(ptr, size, zone);
   };
-
-  base::allocator::ReplaceFunctionsForStoredZones(&new_functions);
+  return new_functions;
 }
 
 }  // namespace allocator