tools/gn: Convert for loops to use the new range-based loops in C++11.

tools/gn/err.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/err.h"
 
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/input_file.h"
@@ skipping 46 matching lines @@
 void OutputHighlighedPosition(const Location& location,
                               const Err::RangeList& ranges,
                               size_t line_length) {
   // Make a buffer of the line in spaces.
   std::string highlight;
   highlight.resize(line_length);
   for (size_t i = 0; i < line_length; i++)
     highlight[i] = ' ';
 
   // Highlight all the ranges on the line.
-  for (size_t i = 0; i < ranges.size(); i++)
-    FillRangeOnLine(ranges[i], location.line_number(), &highlight);
+  for (auto& range : ranges)
+    FillRangeOnLine(range, location.line_number(), &highlight);
 
   // Allow the marker to be one past the end of the line for marking the end.
   highlight.push_back(' ');
   CHECK(location.char_offset() - 1 >= 0 &&
         location.char_offset() - 1 < static_cast<int>(highlight.size()));
   highlight[location.char_offset() - 1] = '^';
 
   // Trim unused spaces from end of line.
   while (!highlight.empty() && highlight[highlight.size() - 1] == ' ')
     highlight.resize(highlight.size() - 1);
@@ skipping 103 matching lines @@
   }
 
   // Optional help text.
   if (!help_text_.empty())
     OutputString(help_text_ + "\n");
 
   // Sub errors.
   for (const auto& sub_err : sub_errs_)
     sub_err.InternalPrintToStdout(true);
 }