mac: Prepare for -Wunused-functions.

chrome/browser/metrics/thread_watcher.cc

 // Copyright (c) 2012 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 "chrome/browser/metrics/thread_watcher.h"
 
 #include <math.h>  // ceil
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
@@ skipping 21 matching lines @@
 
 // The following are unique function names for forcing the crash when a thread
 // is unresponsive. This makes it possible to tell from the callstack alone what
 // thread was unresponsive.
 //
 // We disable optimizations for this block of functions so the compiler doesn't
 // merge them all together.
 MSVC_DISABLE_OPTIMIZE()
 MSVC_PUSH_DISABLE_WARNING(4748)
 
+#ifndef NDEBUG
 int* NullPointer() {
   return reinterpret_cast<int*>(NULL);
 }
+#endif
 
 void NullPointerCrash(int line_number) {
 #ifndef NDEBUG
   *NullPointer() = line_number;  // Crash.
 #else
   logging::DumpWithoutCrashing();
 #endif
 }
 
 NOINLINE void ShutdownCrash() {
@@ skipping 926 matching lines @@
 
 #if defined(OS_WIN)
   // On Windows XP, give twice the time for shutdown.
   if (base::win::GetVersion() <= base::win::VERSION_XP)
     actual_duration *= 2;
 #endif
 
   shutdown_watchdog_ = new ShutdownWatchDogThread(actual_duration);
   shutdown_watchdog_->Arm();
 }