Replace more for loops in GN

tools/gn/command_args.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 <stdio.h>
 #include <stdlib.h>
 
 #include <map>
 
 #include "base/command_line.h"
@@ skipping 110 matching lines @@
   Scope::KeyValueMap build_args;
   setup->build_settings().build_args().MergeDeclaredArguments(&build_args);
 
   // Find all of the arguments we care about. Use a regular map so they're
   // sorted nicely when we write them out.
   std::map<base::StringPiece, Value> sorted_args;
   std::string list_value =
       base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(kSwitchList);
   if (list_value.empty()) {
     // List all values.
-    for (Scope::KeyValueMap::const_iterator i = build_args.begin();
-         i != build_args.end(); ++i)
-      sorted_args.insert(*i);
+    for (const auto& arg : build_args)
+      sorted_args.insert(arg);
   } else {
     // List just the one specified as the parameter to --list.
     Scope::KeyValueMap::const_iterator found_arg = build_args.find(list_value);
     if (found_arg == build_args.end()) {
       Err(Location(), "Unknown build argument.",
           "You asked for \"" + list_value + "\" which I didn't find in any "
           "build file\nassociated with this build.").PrintToStdout();
       return 1;
     }
     sorted_args.insert(*found_arg);
   }
 
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(kSwitchShort)) {
     // Short key=value output.
-    for (std::map<base::StringPiece, Value>::iterator i = sorted_args.begin();
-         i != sorted_args.end(); ++i) {
-      OutputString(i->first.as_string());
+    for (const auto& arg : sorted_args) {
+      OutputString(arg.first.as_string());
       OutputString(" = ");
-      OutputString(i->second.ToString(true));
+      OutputString(arg.second.ToString(true));
       OutputString("\n");
     }
     return 0;
   }
 
   // Long output.
-  for (std::map<base::StringPiece, Value>::iterator i = sorted_args.begin();
-       i != sorted_args.end(); ++i) {
-    PrintArgHelp(i->first, i->second);
+  for (const auto& arg : sorted_args) {
+    PrintArgHelp(arg.first, arg.second);
     OutputString("\n");
   }
 
   return 0;
 }
 
 #if defined(OS_WIN)
 
 bool RunEditor(const base::FilePath& file_to_edit) {
   SHELLEXECUTEINFO info;
@@ skipping 166 matching lines @@
         "Or see \"gn help args\" for more variants.").PrintToStdout();
     return 1;
   }
 
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(kSwitchList))
     return ListArgs(args[0]);
   return EditArgsFile(args[0]);
 }
 
 }  // namespace commands