mac: Remove some 10.6-SDK-only sandbox code.

sandbox/mac/xpc.cc

-// Copyright 2014 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 "sandbox/mac/xpc.h"
-
-namespace sandbox {
-
-bool InitializeXPC() {
-#if !defined(MAC_OS_X_VERSION_10_7) || \
-    MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_7
-  std::vector<std::string> path_list;
-  path_list.push_back("/usr/lib/system/libxpc.dylib");
-
-  sandbox_mac::StubPathMap path_map;
-  path_map[sandbox_mac::kModuleXpc_stubs] = path_list;
-  path_map[sandbox_mac::kModuleXpc_private_stubs] = path_list;
-
-  return sandbox_mac::InitializeStubs(path_map);
-#else
-  return true;
-#endif
-}
-
-}  // namespace sandbox