[Extensions] Add extension feature generation code

extensions/common/features/api_feature.cc

 // Copyright 2014 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 "extensions/common/features/api_feature.h"
 
 namespace extensions {
 
-APIFeature::APIFeature()
-    : internal_(false) {}
+APIFeature::APIFeature() {}
 
 APIFeature::~APIFeature() {
 }
 
-bool APIFeature::IsInternal() const {
-  return internal_;
-}
-
 std::string APIFeature::Parse(const base::DictionaryValue* value) {
   std::string error = SimpleFeature::Parse(value);
   if (!error.empty())
     return error;
 
-  value->GetBoolean("internal", &internal_);
+  bool internal = false;
+  if (value->GetBoolean("internal", &internal))
+    set_internal(internal);
 
-  if (contexts()->empty())
+  if (contexts().empty())
     return name() + ": API features must specify at least one context.";
 
   return std::string();
 }
 
 }  // namespace extensions