Replace more for loops in GN

tools/gn/setup.cc

 // Copyright (c) 2013 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/setup.h"
 
 #include <stdlib.h>
 
 #include <algorithm>
 #include <sstream>
@@ skipping 333 matching lines @@
   // Save the result of the command args.
   Scope::KeyValueMap overrides;
   arg_scope.GetCurrentScopeValues(&overrides);
   build_settings_.build_args().AddArgOverrides(overrides);
   return true;
 }
 
 bool Setup::SaveArgsToFile() {
   ScopedTrace setup_trace(TraceItem::TRACE_SETUP, "Save args file");
 
-  Scope::KeyValueMap args = build_settings_.build_args().GetAllOverrides();
-
   std::ostringstream stream;
-  for (Scope::KeyValueMap::const_iterator i = args.begin();
-       i != args.end(); ++i) {
-    stream << i->first.as_string() << " = " << i->second.ToString(true);
+  for (const auto& pair : build_settings_.build_args().GetAllOverrides()) {
+    stream << pair.first.as_string() << " = " << pair.second.ToString(true);
     stream << std::endl;
   }
 
   // For the first run, the build output dir might not be created yet, so do
   // that so we can write a file into it. Ignore errors, we'll catch the error
   // when we try to write a file to it below.
   base::FilePath build_arg_file =
       build_settings_.GetFullPath(GetBuildArgFile());
   base::CreateDirectory(build_arg_file.DirName());
 
@@ skipping 237 matching lines @@
 }
 
 void DependentSetup::RunPreMessageLoop() {
   CommonSetup::RunPreMessageLoop();
 }
 
 bool DependentSetup::RunPostMessageLoop() {
   return CommonSetup::RunPostMessageLoop();
 }