tools/gn: Change auto to not deduce raw pointers.

tools/gn/xcode_writer.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 "tools/gn/xcode_writer.h"
 
 #include <iomanip>
 #include <map>
 #include <memory>
 #include <sstream>
@@ skipping 401 matching lines @@
       << "\tobjectVersion = 46;\n"
       << "\tobjects = {\n";
 
   for (auto& pair : CollectPBXObjectsPerClass(project)) {
     out << "\n"
         << "/* Begin " << ToString(pair.first) << " section */\n";
     std::sort(pair.second.begin(), pair.second.end(),
               [](const PBXObject* a, const PBXObject* b) {
                 return a->id() < b->id();
               });
-    for (const auto& object : pair.second) {
+    for (auto* object : pair.second) {
       object->Print(out, 2);
     }
     out << "/* End " << ToString(pair.first) << " section */\n";
   }
 
   out << "\t};\n"
       << "\trootObject = " << project->Reference() << ";\n"
       << "}\n";
 }