Replace more for loops in GN

tools/gn/operators.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/operators.h"
 
 #include "base/strings/string_number_conversions.h"
 #include "tools/gn/err.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/scope.h"
@@ skipping 18 matching lines @@
       dest->list_value().push_back(source);
     return;
   }
   if (source.type() != Value::LIST) {
     // Any non-list and non-string being added to a list can just get appended,
     // we're not going to filter it.
     dest->list_value().push_back(source);
     return;
   }
 
-  const std::vector<Value>& source_list = source.list_value();
   if (!filter || filter->is_empty()) {
     // No filter, append everything.
-    for (size_t i = 0; i < source_list.size(); i++)
-      dest->list_value().push_back(source_list[i]);
+    for (const auto& source_entry : source.list_value())
+      dest->list_value().push_back(source_entry);
     return;
   }
 
   // Note: don't reserve() the dest vector here since that actually hurts
   // the allocation pattern when the build script is doing multiple small
   // additions.
-  for (size_t i = 0; i < source_list.size(); i++) {
-    if (!filter->MatchesValue(source_list[i]))
-      dest->list_value().push_back(source_list[i]);
+  for (const auto& source_entry : source.list_value()) {
+    if (!filter->MatchesValue(source_entry))
+      dest->list_value().push_back(source_entry);
   }
 }
 
 Value GetValueOrFillError(const BinaryOpNode* op_node,
                           const ParseNode* node,
                           const char* name,
                           Scope* scope,
                           Err* err) {
   Value value = node->Execute(scope, err);
   if (err->has_error())
@@ skipping 158 matching lines @@
 
     // Left-hand-side list.
     case Value::LIST:
       switch (right.type()) {
         case Value::LIST:  // list + list -> list concat.
           if (left_token.value() == kSourcesName) {
             // Filter additions through the assignment filter.
             AppendFilteredSourcesToValue(scope, right, left);
           } else {
             // Normal list concat.
-            for (size_t i = 0; i < right.list_value().size(); i++)
-              left->list_value().push_back(right.list_value()[i]);
+            for (const auto& value : right.list_value())
+              left->list_value().push_back(value);
           }
           return;
 
         default:
           *err = Err(op_node->op(), "Incompatible types to add.",
               "To append a single item to a list do \"foo += [ bar ]\".");
           return;
       }
 
     default:
@@ skipping 370 matching lines @@
     return ExecuteGreaterEquals(scope, op_node, left_value, right_value, err);
   if (op.type() == Token::LESS_EQUAL)
     return ExecuteLessEquals(scope, op_node, left_value, right_value, err);
   if (op.type() == Token::GREATER_THAN)
     return ExecuteGreater(scope, op_node, left_value, right_value, err);
   if (op.type() == Token::LESS_THAN)
     return ExecuteLess(scope, op_node, left_value, right_value, err);
 
   return Value();
 }