mac: Hook up allocator shim during app startup.

base/allocator/allocator_shim.cc

 // Copyright 2016 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_shim.h"
 
 #include <errno.h>
 
 #include <new>
 
@@ skipping 72 matching lines @@
       subtle::NoBarrier_Load(&g_chain_head)
 #endif
   );
 }
 
 }  // namespace
 
 namespace base {
 namespace allocator {
 
+#if defined(OS_MACOSX)
+bool g_is_mac_shim_layer_initialized = false;
+#endif
+
 void SetCallNewHandlerOnMallocFailure(bool value) {
   g_call_new_handler_on_malloc_failure = value;
 }
 
 void* UncheckedAlloc(size_t size) {
   const allocator::AllocatorDispatch* const chain_head = GetChainHead();
   return chain_head->alloc_function(chain_head, size);
 }
 
 void InsertAllocatorDispatch(AllocatorDispatch* dispatch) {
@@ skipping 195 matching lines @@
 namespace base {
 namespace allocator {
 void InitializeAllocatorShim() {
   // Prepares the default dispatch. After the intercepted malloc calls have
   // traversed the shim this will route them to the default malloc zone.
   InitializeDefaultDispatchToMacAllocator();
 
   // This replaces the default malloc zone, causing calls to malloc & friends
   // from the codebase to be routed to ShimMalloc() above.
   OverrideMacSymbols();
+
+  g_is_mac_shim_layer_initialized = true;
 }
 }  // namespace allocator
 }  // namespace base
 #endif
 
 // Cross-checks.
 
 #if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
 #error The allocator shim should not be compiled when building for memory tools.
 #endif
 
 #if (defined(__GNUC__) && defined(__EXCEPTIONS)) || \
     (defined(_HAS_EXCEPTIONS) && _HAS_EXCEPTIONS)
 #error This code cannot be used when exceptions are turned on.
 #endif