Pass a Feature* to IsAnyFeatureAvailableToContext instead of a string name.

chrome/common/extensions/features/base_feature_provider.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_BASE_FEATURE_PROVIDER_H_
 #define CHROME_COMMON_EXTENSIONS_FEATURES_BASE_FEATURE_PROVIDER_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 13 matching lines @@
   // Creates a new BaseFeatureProvider. Pass null to |factory| to have the
   // provider create plain old Feature instances.
   BaseFeatureProvider(const base::DictionaryValue& root,
                       FeatureFactory factory);
   virtual ~BaseFeatureProvider();
 
   // Gets a feature provider for a specific feature type, like "permission".
   static FeatureProvider* GetByName(const std::string& name);
 
   // Gets the feature |feature_name|, if it exists.
-  virtual Feature* GetFeature(const std::string& feature_name) OVERRIDE;
-  virtual Feature* GetParent(Feature* feature) OVERRIDE;
+  virtual Feature* GetFeature(const std::string& feature_name) const OVERRIDE;
+  virtual Feature* GetParent(Feature* feature) const OVERRIDE;
 
-  virtual const std::vector<std::string>& GetAllFeatureNames() OVERRIDE;
+  virtual const std::vector<std::string>& GetAllFeatureNames() const OVERRIDE;
 
  private:
   typedef std::map<std::string, linked_ptr<Feature> > FeatureMap;
   FeatureMap features_;
 
-  std::vector<std::string> feature_names_;
+  // Populated on first use.
+  mutable std::vector<std::string> feature_names_;
 
   FeatureFactory factory_;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_FEATURES_BASE_FEATURE_PROVIDER_H_