Implement API features for the Extension API feature system

chrome/common/extensions/features/simple_feature.h

 // Copyright (c) 2012 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 CHROME_COMMON_EXTENSIONS_FEATURES_SIMPLE_FEATURE_H_
 #define CHROME_COMMON_EXTENSIONS_FEATURES_SIMPLE_FEATURE_H_
 
 #include <set>
 #include <string>
 
@@ skipping 12 matching lines @@
  public:
   SimpleFeature();
   SimpleFeature(const SimpleFeature& other);
   virtual ~SimpleFeature();
 
   std::set<std::string>* whitelist() { return &whitelist_; }
   std::set<Manifest::Type>* extension_types() { return &extension_types_; }
 
   // Parses the JSON representation of a feature into the fields of this object.
   // Unspecified values in the JSON are not modified in the object. This allows
-  // us to implement inheritance by parsing one value after another.
-  void Parse(const DictionaryValue* value);
+  // us to implement inheritance by parsing one value after another. Returns
+  // the error found, or an empty string on success.
+  virtual std::string Parse(const DictionaryValue* value);
 
   // Returns true if the feature contains the same values as another.
   bool Equals(const SimpleFeature& other) const;
 
   Location location() const { return location_; }
   void set_location(Location location) { location_ = location; }
 
   Platform platform() const { return platform_; }
   void set_platform(Platform platform) { platform_ = platform; }
 
@@ skipping 62 matching lines @@
   int min_manifest_version_;
   int max_manifest_version_;
   chrome::VersionInfo::Channel channel_;
 
   FRIEND_TEST_ALL_PREFIXES(ExtensionSimpleFeatureTest, Context);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_FEATURES_SIMPLE_FEATURE_H_