Load extensions features file separately when needed

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 <set>
 #include <string>
 
 #include "base/memory/linked_ptr.h"
 #include "base/values.h"
 #include "chrome/common/extensions/features/feature_provider.h"
 #include "chrome/common/extensions/features/simple_feature.h"
 
 namespace extensions {
 
 // Reads Features out of a simple JSON file description.
 class BaseFeatureProvider : public FeatureProvider {
  public:
   typedef SimpleFeature*(*FeatureFactory)();
 
   // Creates a new BaseFeatureProvider. Pass null to |factory| to have the
   // provider create plain old Feature instances.
   BaseFeatureProvider(const DictionaryValue& root, FeatureFactory factory);
   virtual ~BaseFeatureProvider();
 
-  // Gets an instance for the _api_features.json file that is baked into
-  // Chrome as a resource.
-  static BaseFeatureProvider* GetAPIFeatures();
-
-  // Gets an instance for the _manifest_features.json file that is baked into
-  // Chrome as a resource.
-  static BaseFeatureProvider* GetManifestFeatures();
-
-  // Gets an instance for the _permission_features.json file that is baked into
-  // Chrome as a resource.
-  static BaseFeatureProvider* GetPermissionFeatures();
+  // Use GetFeaturesByName() to get the BaseFeatureProvider for a specific type.
+  // If it is possible that the feature provider will not be used, use
+  // LazyGetFeaturesByName().
+  static BaseFeatureProvider* GetFeaturesByName(const std::string& name);
+  static FeatureProvider* LazyGetFeaturesByName(const std::string& name);

[not at google - send to devlin, 2013/04/10 02:06:22]

Is there really a difference? Can you combine these into a single method (also
I'd call it GetByName) and make that the lazy version?

[cduvall, 2013/04/10 02:26:12]

They're both needed because GetFeaturesByName() returns a BaseFeatureProvider,
which is used in some places for BaseFeatureProvider::GetAllFeatureNames().
LazyGetFeaturesByName() just returns a standard FeatureProvider, which just has
GetFeature().

I renamed to GetByName() and GetBaseFeatureProviderByName(), which is a little
verbose (any better ideas?)

[not at google - send to devlin, 2013/04/10 02:42:13]

Ah ok. Perhaps we should pull GetAllFeatureNames into the FeatureProvider
interface then.

[cduvall, 2013/04/10 02:57:56]

Done, had to take off the const, because it wouldn't work for the
LazyFeatureProvider.

 
   // Returns all features described by this instance.
   std::set<std::string> GetAllFeatureNames() const;
 
   // Gets the feature |feature_name|, if it exists.
   virtual Feature* GetFeature(const std::string& feature_name) OVERRIDE;
 
  private:
   typedef std::map<std::string, linked_ptr<Feature> > FeatureMap;
   FeatureMap features_;
 
   FeatureFactory factory_;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_FEATURES_BASE_FEATURE_PROVIDER_H_