[Extensions] Break up BaseFeatureProvider, create JSONFeatureProvider

extensions/common/features/json_feature_provider.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_JSON_FEATURE_PROVIDER_H_
+#define EXTENSIONS_COMMON_FEATURES_JSON_FEATURE_PROVIDER_H_
+
+#include "extensions/common/features/base_feature_provider.h"
+
+namespace base {
+class DictionaryValue;
+}
+
+namespace extensions {
+class SimpleFeature;
+
+// Reads Features out of a simple JSON file description.
+class JSONFeatureProvider : public BaseFeatureProvider {
+ public:
+  typedef SimpleFeature* (*FeatureFactory)();
+
+  // Creates a new JSONFeatureProvider. Pass null to |factory| to have the
+  // provider create plain old Feature instances.
+  JSONFeatureProvider(const base::DictionaryValue& root,
+                      FeatureFactory factory);
+  ~JSONFeatureProvider() override;
+
+ private:
+  FeatureFactory factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(JSONFeatureProvider);
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_COMMON_FEATURES_JSON_FEATURE_PROVIDER_H_