Replace more for loops in GN

tools/gn/function_toolchain.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 <algorithm>
 #include <limits>
 
 #include "tools/gn/err.h"
 #include "tools/gn/functions.h"
 #include "tools/gn/parse_tree.h"
@@ skipping 44 matching lines @@
   (tool->*set)(v->string_value());
   return true;
 }
 
 // Calls the given validate function on each type in the list. On failure,
 // sets the error, blame the value, and return false.
 bool ValidateSubstitutionList(const std::vector<SubstitutionType>& list,
                               bool (*validate)(SubstitutionType),
                               const Value* origin,
                               Err* err) {
-  for (size_t i = 0; i < list.size(); i++) {
-    SubstitutionType cur_type = list[i];
+  for (const auto& cur_type : list) {
     if (!validate(cur_type)) {
       *err = Err(*origin, "Pattern not valid here.",
           "You used the pattern " + std::string(kSubstitutionNames[cur_type]) +
           " which is not valid\nfor this variable.");
       return false;
     }
   }
   return true;
 }
 
@@ skipping 95 matching lines @@
 }
 
 bool IsLinkerTool(Toolchain::ToolType type) {
   return type == Toolchain::TYPE_ALINK ||
          type == Toolchain::TYPE_SOLINK ||
          type == Toolchain::TYPE_LINK;
 }
 
 bool IsPatternInOutputList(const SubstitutionList& output_list,
                            const SubstitutionPattern& pattern) {
-  for (size_t output_i = 0; output_i < output_list.list().size(); output_i++) {
-    const SubstitutionPattern& cur = output_list.list()[output_i];
+  for (const auto& cur : output_list.list()) {
     if (pattern.ranges().size() == cur.ranges().size() &&
         std::equal(pattern.ranges().begin(), pattern.ranges().end(),
                    cur.ranges().begin()))
       return true;
   }
   return false;
 }
 
 }  // namespace
 
@@ skipping 719 matching lines @@
     return Value();
 
   Scope::KeyValueMap values;
   block_scope.GetCurrentScopeValues(&values);
   toolchain->args() = values;
 
   return Value();
 }
 
 }  // namespace functions