Replace more for loops in GN

tools/gn/value_extractors.cc

Index: tools/gn/value_extractors.cc
diff --git a/tools/gn/value_extractors.cc b/tools/gn/value_extractors.cc
index fe86bd3d61d88f4adfaf37eac14f823149608a24..9e6a37edc95c6c27478b0434ddc7f49d6ad9d645 100644
--- a/tools/gn/value_extractors.cc
+++ b/tools/gn/value_extractors.cc
@@ -42,13 +42,13 @@ bool ListValueUniqueExtractor(const Value& value,
     return false;
   const std::vector<Value>& input_list = value.list_value();
 
-  for (size_t i = 0; i < input_list.size(); i++) {
+  for (const auto& item : input_list) {
     T new_one;
-    if (!converter(input_list[i], &new_one, err))
+    if (!converter(item, &new_one, err))
       return false;
     if (!dest->push_back(new_one)) {
       // Already in the list, throw error.
-      *err = Err(input_list[i], "Duplicate item in list");
+      *err = Err(item, "Duplicate item in list");
       size_t previous_index = dest->IndexOf(new_one);
       err->AppendSubErr(Err(input_list[previous_index],
                             "This was the previous definition."));
@@ -143,10 +143,10 @@ bool ExtractListOfStringValues(const Value& value,
     return false;
   const std::vector<Value>& input_list = value.list_value();
   dest->reserve(input_list.size());
-  for (size_t i = 0; i < input_list.size(); i++) {
-    if (!input_list[i].VerifyTypeIs(Value::STRING, err))
+  for (const auto& item : input_list) {
+    if (!item.VerifyTypeIs(Value::STRING, err))
       return false;
-    dest->push_back(input_list[i].string_value());
+    dest->push_back(item.string_value());
   }
   return true;
 }