Add a declarative way in c/b/s/sync_prefs.cc to say which data types have prefs

chrome/browser/sync/sync_prefs.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_SYNC_SYNC_PREFS_H_
 #define CHROME_BROWSER_SYNC_SYNC_PREFS_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
@@ skipping 100 matching lines @@
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
   // For testing.
 
   void SetManagedForTest(bool is_managed);
   syncable::ModelTypeSet GetAcknowledgeSyncedTypesForTest() const;
 
  private:
+  void RegisterPrefGroups();
   void RegisterPreferences();
 
   void RegisterDataTypePreferredPref(
       syncable::ModelType type, bool is_preferred);
   bool GetDataTypePreferred(syncable::ModelType type) const;
   void SetDataTypePreferred(syncable::ModelType type, bool is_preferred);
 
+  // Returns a ModelTypeSet based on |types| expanded to include pref groups
+  // (see |pref_groups_|), but as a subset of |registered_types|.
+  syncable::ModelTypeSet ResolvePrefGroups(
+      syncable::ModelTypeSet registered_types,
+      syncable::ModelTypeSet types) const;
+
   base::NonThreadSafe non_thread_safe_;
 
   // May be NULL.
   PrefService* const pref_service_;
 
   ObserverList<SyncPrefObserver> sync_pref_observers_;
 
   // The preference that controls whether sync is under control by
   // configuration management.
   BooleanPrefMember pref_sync_managed_;
 
+  // Groups of prefs that always have the same value as a "master" pref.
+  // For example, the APPS group has {APP_NOTIFICATIONS, APP_SETTINGS}
+  // (as well as APPS, but that is implied), so
+  //   pref_groups_[syncable::APPS] =       { syncable::APP_NOTIFICATIONS,
+  //                                          syncable::APP_SETTINGS }
+  //   pref_groups_[syncable::EXTENSIONS] = { syncable::EXTENSION_SETTINGS }
+  // etc.
+  typedef std::map<syncable::ModelType, syncable::ModelTypeSet> PrefGroupsMap;
+  PrefGroupsMap pref_groups_;
+
   DISALLOW_COPY_AND_ASSIGN(SyncPrefs);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_SYNC_PREFS_H_