sync: deferred initialization support for app/extension settings

chrome/browser/extensions/api/storage/settings_backend.h

Index: chrome/browser/extensions/api/storage/settings_backend.h
diff --git a/chrome/browser/extensions/api/storage/settings_backend.h b/chrome/browser/extensions/api/storage/settings_backend.h
index 1706828b356f6ef4d3d696ea9d07fdb664d90f08..8fe9108fbda7b93ec153ba2f38f4325ca185101d 100644
--- a/chrome/browser/extensions/api/storage/settings_backend.h
+++ b/chrome/browser/extensions/api/storage/settings_backend.h
@@ -40,6 +40,7 @@ class SettingsBackend : public syncer::SyncableService {
   SettingsBackend(
       const scoped_refptr<SettingsStorageFactory>& storage_factory,
       const base::FilePath& base_path,
+      syncer::ModelType sync_type,
       const SettingsStorageQuotaEnforcer::Limits& quota,
       const scoped_refptr<SettingsObserverList>& observers);
 
@@ -65,6 +66,11 @@ class SettingsBackend : public syncer::SyncableService {
       const syncer::SyncChangeList& change_list) OVERRIDE;
   virtual void StopSyncing(syncer::ModelType type) OVERRIDE;
 
+  // Provides a StartSyncFlare to the SyncableService. See
+  // sync_start_util for more.
+  void InjectStartSyncFlare(
+      const syncer::SyncableService::StartSyncFlare& flare);
+
  private:
   // Gets a weak reference to the storage area for a given extension,
   // initializing sync with some initial data if sync enabled.
@@ -98,8 +104,7 @@ class SettingsBackend : public syncer::SyncableService {
       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.
+  // Current sync model type. Either EXTENSION_SETTINGS or APP_SETTINGS.
   syncer::ModelType sync_type_;
 
   // Current sync processor, if any.
@@ -108,6 +113,8 @@ class SettingsBackend : public syncer::SyncableService {
   // Current sync error handler if any.
   scoped_ptr<syncer::SyncErrorFactory> sync_error_factory_;
 
+  syncer::SyncableService::StartSyncFlare flare_;
+
   DISALLOW_COPY_AND_ASSIGN(SettingsBackend);
 };