Use mach_override to intercept all newly registered malloc zones.

base/allocator/allocator_interception_mac_unittest.cc

Index: base/allocator/allocator_interception_mac_unittest.cc
diff --git a/base/allocator/allocator_interception_mac_unittest.cc b/base/allocator/allocator_interception_mac_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..95e026bd1c5ef0863bf9e4abe6ce36ab0f013f6e
--- /dev/null
+++ b/base/allocator/allocator_interception_mac_unittest.cc
@@ -0,0 +1,44 @@
+// 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.
+
+#include "base/allocator/allocator_interception_mac.h"
+#include "base/allocator/malloc_zone_functions_mac.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/apple_apsl/malloc.h"
+
+namespace base {
+namespace allocator {
+
+namespace {
+void* TestMalloc(struct _malloc_zone_t* zone, size_t size) {
+  return reinterpret_cast<void*>(0x123);
+}
+}  // namespace
+
+class AllocatorInterceptionMacTest : public testing::Test {
+ protected:
+  void TearDown() override { UninterceptMallocZonesForTesting(); }
+};
+
+TEST_F(AllocatorInterceptionMacTest, InterceptNewlyRegisteredZone) {
+  ChromeMallocZone* default_zone =
+      reinterpret_cast<ChromeMallocZone*>(malloc_default_zone());
+  MallocZoneFunctions default_zone_functions;
+  StoreZoneFunctions(default_zone, &default_zone_functions);
+  default_zone_functions.malloc = &TestMalloc;
+  InterceptNewlyRegisteredMallocZones(&default_zone_functions);
+
+  struct _malloc_zone_t* test_malloc_zone = malloc_create_zone(0, 0);
+  ChromeMallocZone* test_zone =
+      reinterpret_cast<ChromeMallocZone*>(test_malloc_zone);
+  EXPECT_EQ(test_zone->malloc, &TestMalloc);
+
+  void* result = malloc_zone_malloc(test_malloc_zone, 13);
+  EXPECT_EQ(reinterpret_cast<void*>(0x123), result);
+
+  malloc_destroy_zone(test_malloc_zone);
+}
+
+}  // namespace allocator
+}  // namespace base