Replace more for loops in GN

tools/gn/value.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/value.h"
 
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "tools/gn/scope.h"
 
@@ skipping 134 matching lines @@
       result.push_back(']');
       return result;
     }
     case SCOPE: {
       Scope::KeyValueMap scope_values;
       scope_value_->GetCurrentScopeValues(&scope_values);
       if (scope_values.empty())
         return std::string("{ }");
 
       std::string result = "{\n";
-      for (Scope::KeyValueMap::const_iterator i = scope_values.begin();
-           i != scope_values.end(); ++i) {
-        result += "  " + i->first.as_string() + " = " +
-                  i->second.ToString(true) + "\n";
+      for (const auto& pair : scope_values) {
+        result += "  " + pair.first.as_string() + " = " +
+                  pair.second.ToString(true) + "\n";
       }
       result += "}";
 
       return result;
     }
   }
   return std::string();
 }
 
 bool Value::VerifyTypeIs(Type t, Err* err) const {
@@ skipping 32 matching lines @@
       // iteration code.
       return false;
     default:
       return false;
   }
 }
 
 bool Value::operator!=(const Value& other) const {
   return !operator==(other);
 }