Replace more for loops in GN

tools/gn/gn_main.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 "base/at_exit.h"
 #include "base/command_line.h"
 #include "base/strings/utf_string_conversions.h"
 #include "tools/gn/commands.h"
 #include "tools/gn/err.h"
 #include "tools/gn/location.h"
 #include "tools/gn/standard_out.h"
 
 // Only the GN-generated build makes this header for now.
 // TODO(brettw) consider adding this if we need it in GYP.
 #if defined(GN_BUILD)
 #include "tools/gn/last_commit_position.h"
 #else
 #define LAST_COMMIT_POSITION "UNKNOWN"
 #endif
 
 namespace {
 
 std::vector<std::string> GetArgs(const CommandLine& cmdline) {
   CommandLine::StringVector in_args = cmdline.GetArgs();
 #if defined(OS_WIN)
   std::vector<std::string> out_args;
-  for (size_t i = 0; i < in_args.size(); i++)
-    out_args.push_back(base::WideToUTF8(in_args[i]));
+  for (const auto& arg : in_args)
+    out_args.push_back(base::WideToUTF8(arg));
   return out_args;
 #else
   return in_args;
 #endif
 }
 
 }  // namespace
 
 int main(int argc, char** argv) {
   base::AtExitManager at_exit;
@@ skipping 33 matching lines @@
     retval = found_command->second.runner(args);
   } else {
     Err(Location(),
         "Command \"" + command + "\" unknown.").PrintToStdout();
     commands::RunHelp(std::vector<std::string>());
     retval = 1;
   }
 
   exit(retval);  // Don't free memory, it can be really slow!
 }