Separate the syncing of extension settings and app settings into separate data

chrome/browser/extensions/syncable_extension_settings_storage.h

Index: chrome/browser/extensions/syncable_extension_settings_storage.h
diff --git a/chrome/browser/extensions/syncable_extension_settings_storage.h b/chrome/browser/extensions/syncable_extension_settings_storage.h
index 499d89c3ff5957ce26a62bcff79a83105f854bbc..d222987e6f56c67fab062a2779300f25e3b27388 100644
--- a/chrome/browser/extensions/syncable_extension_settings_storage.h
+++ b/chrome/browser/extensions/syncable_extension_settings_storage.h
@@ -41,6 +41,8 @@ class SyncableExtensionSettingsStorage : public ExtensionSettingsStorage {
   // Sync-related methods, analogous to those on SyncableService (handled by
   // ExtensionSettings).
   SyncError StartSyncing(
+      // Either EXTENSION_SETTINGS or APP_SETTINGS.
+      syncable::ModelType type,
       const DictionaryValue& sync_state,
       // Must NOT be NULL. Ownership NOT taken.
       SyncChangeProcessor* sync_processor);
@@ -92,6 +94,10 @@ class SyncableExtensionSettingsStorage : public ExtensionSettingsStorage {
   // Storage area to sync.
   const scoped_ptr<ExtensionSettingsStorage> delegate_;
 
+  // Sync model type.  Either EXTENSION_SETTINGS or APP_SETTINGS while sync is
+  // enabled (between calls to Start/StopSyncing), or UNSPECIFIED while not.
+  syncable::ModelType sync_type_;
+
   // Sync processor.  Non-NULL while sync is enabled (between calls to
   // StartSyncing and StopSyncing).
   SyncChangeProcessor* sync_processor_;