Extension Settings API: make it so that when leveldb storage areas fail to be

chrome/browser/extensions/settings/settings_backend.h

 // Copyright (c) 2011 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_BROWSER_EXTENSIONS_SETTINGS_SETTINGS_BACKEND_H_
 #define CHROME_BROWSER_EXTENSIONS_SETTINGS_SETTINGS_BACKEND_H_
 #pragma once
 
 #include "base/compiler_specific.h"
 #include "base/file_path.h"
 #include "base/memory/linked_ptr.h"
 #include "base/memory/ref_counted.h"
 #include "base/observer_list_threadsafe.h"
 #include "base/task.h"
+#include "chrome/browser/extensions/settings/settings_leveldb_storage.h"
 #include "chrome/browser/extensions/settings/settings_observer.h"
 #include "chrome/browser/extensions/settings/syncable_settings_storage.h"
 #include "chrome/browser/sync/api/syncable_service.h"
 
 namespace extensions {
 
 // Manages SettingsStorage objects for extensions, including routing
 // changes from sync to them.
 // Lives entirely on the FILE thread.
 class SettingsBackend : public SyncableService {
  public:
+  // |storage_factory| is use to create leveldb storage areas.
   // |base_path| is the base of the extension settings directory, so the
   // databases will be at base_path/extension_id.
   // |observers| is the list of observers to settings changes.
   explicit SettingsBackend(
+      // Ownership NOT taken.
+      SettingsStorageFactory* storage_factory,
       const FilePath& base_path,
       const scoped_refptr<SettingsObserverList>& observers);
 
   virtual ~SettingsBackend();
 
   // Gets a weak reference to the storage area for a given extension.
   // Must be run on the FILE thread.
   //
   // By default this will be an SettingsLeveldbStorage, but on
   // failure to create a leveldb instance will fall back to
@@ skipping 21 matching lines @@
   //
   // By default this will be of a cached LEVELDB storage, but on failure to
   // create a leveldb instance will fall back to cached NOOP storage.
   SyncableSettingsStorage* GetOrCreateStorageWithSyncData(
       const std::string& extension_id, const DictionaryValue& sync_data) const;
 
   // Gets all extension IDs known to extension settings.  This may not be all
   // installed extensions.
   std::set<std::string> GetKnownExtensionIDs() const;
 
+  // The Factory to use for creating leveldb storage areas.  Not owned.
+  SettingsStorageFactory* const storage_factory_;

[Matt Perry, 2011/11/11 00:49:38]

Is there a reason this is const? This will just prevent you from pointing
storage_factory_ at a different object. Did you mean "const
SettingsStorageFactory*" (which will prevent you from modifying the data of the
object being pointed to)?

[not at google - send to devlin, 2011/11/12 02:10:27]

Yep that was deliberate.  It could be "const SettingsStoargeFactory* const
storage_factory_" but "const SettingsStorageFactory" isn't really that
interesting, it would mean I'd need to add const to the ::Create methods, which
is just boring.

I... like to add const to pointers in the same way that I like putting final to
members in Java... just documentation that this won't change.

+
   // The base file path to create any leveldb databases at.
   const FilePath base_path_;
 
   // The list of observers to settings changes.
   const scoped_refptr<SettingsObserverList> observers_;
 
   // A cache of SettingsStorage objects that have already been created.
   // Ensure that there is only ever one created per extension.
   typedef std::map<std::string, linked_ptr<SyncableSettingsStorage> >
       StorageObjMap;
   mutable StorageObjMap storage_objs_;
 
   // Current sync model type.  Will be UNSPECIFIED if sync hasn't been enabled
   // yet, and either SETTINGS or APP_SETTINGS if it has been.
   syncable::ModelType sync_type_;
 
   // Current sync processor, if any.
   SyncChangeProcessor* sync_processor_;
 
   DISALLOW_COPY_AND_ASSIGN(SettingsBackend);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_SETTINGS_SETTINGS_BACKEND_H_