Added check for behavior feature existense

extensions/common/features/feature_provider.h

 // Copyright 2013 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_FEATURE_PROVIDER_H_
 #define EXTENSIONS_COMMON_FEATURES_FEATURE_PROVIDER_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 21 matching lines @@
 
   // Directly access the common FeatureProvider types.
   // Each is equivalent to GetByName('featuretype').
   static const FeatureProvider* GetAPIFeatures();
   static const FeatureProvider* GetManifestFeatures();
   static const FeatureProvider* GetPermissionFeatures();
   static const FeatureProvider* GetBehaviorFeatures();
 
   // Directly get Features from the common FeatureProvider types.
   // Each is equivalent to GetByName('featuretype')->GetFeature(name).
+  // NOTE: These functions may return |nullptr| in case corresponding JSON file
+  // got corrupted.
   static const Feature* GetAPIFeature(const std::string& name);
   static const Feature* GetManifestFeature(const std::string& name);
   static const Feature* GetPermissionFeature(const std::string& name);
   static const Feature* GetBehaviorFeature(const std::string& name);
 
   //
   // Instance methods.
   //
 
   // Returns the feature with the specified name.
   virtual Feature* GetFeature(const std::string& name) const = 0;
 
   // Returns the parent feature of |feature|, or NULL if there isn't one.
   virtual Feature* GetParent(Feature* feature) const = 0;
 
   // Returns the features inside the |parent| namespace, recursively.
   virtual std::vector<Feature*> GetChildren(const Feature& parent) const = 0;
 
   // Returns a map containing all features described by this instance.
   virtual const FeatureMap& GetAllFeatures() const = 0;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_FEATURES_FEATURE_PROVIDER_H_