Replace more for loops in GN

tools/gn/standard_out.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/standard_out.h"
 
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/logging.h"
@@ skipping 149 matching lines @@
                  DECORATION_DIM);
   }
 
   OutputString(line.substr(first_normal) + "\n");
 }
 
 void PrintLongHelp(const std::string& text) {
   std::vector<std::string> lines;
   base::SplitStringDontTrim(text, '\n', &lines);
 
-  for (size_t i = 0; i < lines.size(); i++) {
-    const std::string& line = lines[i];
-
+  for (const auto& line : lines) {
     // Check for a heading line.
     if (!line.empty() && line[0] != ' ') {
       // Highlight up to the colon (if any).
       size_t chars_to_highlight = line.find(':');
       if (chars_to_highlight == std::string::npos)
         chars_to_highlight = line.size();
       OutputString(line.substr(0, chars_to_highlight), DECORATION_YELLOW);
       OutputString(line.substr(chars_to_highlight) + "\n");
       continue;
     }
 
     // Check for a comment.
     TextDecoration dec = DECORATION_NONE;
     for (size_t char_i = 0; char_i < line.size(); char_i++) {
       if (line[char_i] == '#') {
         // Got a comment, draw dimmed.
         dec = DECORATION_DIM;
         break;
       } else if (line[char_i] != ' ') {
         break;
       }
     }
 
     OutputString(line + "\n", dec);
   }
 }