Implement API features for the Extension API feature system

chrome/common/extensions/features/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_FEATURE_H_
 #define CHROME_COMMON_EXTENSIONS_FEATURES_FEATURE_H_
 
 #include <set>
 #include <string>
 
@@ skipping 106 matching lines @@
     ~ScopedCurrentChannel() {
       SetCurrentChannel(original_channel_);
     }
 
    private:
     chrome::VersionInfo::Channel original_channel_;
   };
 
   const std::string& name() const { return name_; }
   void set_name(const std::string& name) { name_ = name; }
+  const std::set<std::string>& dependencies() { return dependencies_; }
 
   // Gets the platform the code is currently running on.
   static Platform GetCurrentPlatform();
 
   // Gets the Feature::Location value for the specified Manifest::Location.
   static Location ConvertLocation(Manifest::Location extension_location);
 
-  // TODO(justinlin): Remove and move to APIFeature when it exists.
   virtual std::set<Context>* GetContexts() = 0;
 
   // Returns true if the feature is available to be parsed into a new extension
   // manifest.
   Availability IsAvailableToManifest(const std::string& extension_id,
                                      Manifest::Type type,
                                      Location location,
                                      int manifest_version) const {
     return IsAvailableToManifest(extension_id, type, location, manifest_version,
                                  GetCurrentPlatform());
@@ skipping 15 matching lines @@
                                             Context context,
                                             const GURL& url,
                                             Platform platform) const = 0;
 
   virtual std::string GetAvailabilityMessage(AvailabilityResult result,
                                              Manifest::Type type,
                                              const GURL& url) const = 0;
 
  protected:
   std::string name_;
+  std::set<std::string> dependencies_;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_FEATURES_FEATURE_H_