[Extensions] Remove JSONFeatureProvider, SimpleFeature::Parse

extensions/common/features/api_feature.h

 // 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.
 
 #ifndef EXTENSIONS_COMMON_FEATURES_API_FEATURE_H_
 #define EXTENSIONS_COMMON_FEATURES_API_FEATURE_H_
 
-#include <string>
-
 #include "extensions/common/features/simple_feature.h"
 
 namespace extensions {
 
-class APIFeature : public SimpleFeature {
- public:
-  APIFeature();
-  ~APIFeature() override;
-
-  // extensions::Feature:
-  bool Validate(std::string* error) override;
-};
+// TODO(devlin): APIFeatures are just SimpleFeatures now. However, there's a
+// bunch of stuff (including the feature compiler) that relies on the presence
+// of an APIFeature class. For now, just typedef this, but eventually we should
+// remove it.
+using APIFeature = SimpleFeature;
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_FEATURES_API_FEATURE_H_