sync: deferred initialization support for app/extension settings

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

 // 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.
 
 #include "chrome/browser/extensions/api/storage/settings_backend.h"
 
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "chrome/browser/extensions/api/storage/settings_sync_processor.h"
 #include "chrome/browser/extensions/api/storage/settings_sync_util.h"
 #include "chrome/browser/extensions/api/storage/syncable_settings_storage.h"
 #include "content/public/browser/browser_thread.h"
 #include "sync/api/sync_error_factory.h"
 
 using content::BrowserThread;
 
 namespace extensions {
 
 SettingsBackend::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)
     : storage_factory_(storage_factory),
       base_path_(base_path),
       quota_(quota),
       observers_(observers),
-      sync_type_(syncer::UNSPECIFIED) {
+      sync_type_(sync_type) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  DCHECK(sync_type_ == syncer::EXTENSION_SETTINGS ||
+         sync_type_ == syncer::APP_SETTINGS);
 }
 
 SettingsBackend::~SettingsBackend() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
 }
 
 ValueStore* SettingsBackend::GetStorage(
     const std::string& extension_id) const {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   DictionaryValue empty;
@@ skipping 23 matching lines @@
           storage));
   storage_objs_[extension_id] = syncable_storage;
 
   if (sync_processor_.get()) {
     syncer::SyncError error =
         syncable_storage->StartSyncing(
             sync_data,
             CreateSettingsSyncProcessor(extension_id).Pass());
     if (error.IsSet())
       syncable_storage.get()->StopSyncing();
+  } else {
+    flare_.Run(sync_type_);

[not at google - send to devlin, 2013/05/20 18:00:04]

what does this actually do? will it call MergeDataAndStartSyncing? synchronously
or asynchronously? a brief comment would be nice to readers.

[tim (not reviewing), 2013/05/20 18:21:15]

Done.

   }
 
   return syncable_storage.get();
 }
 
 void SettingsBackend::DeleteStorage(const std::string& extension_id) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
 
   // Clear settings when the extension is uninstalled.  Leveldb implementations
   // will also delete the database from disk when the object is destroyed as a
@@ skipping 72 matching lines @@
           maybe_settings->error();
       continue;
     }
     AddAllSyncData(*it, *maybe_settings->settings().get(),
                    type, &all_sync_data);
   }
 
   return all_sync_data;
 }
 
+void SettingsBackend::InjectStartSyncFlare(
+    const syncer::SyncableService::StartSyncFlare& flare) {
+  flare_ = flare;
+}
+
 syncer::SyncMergeResult SettingsBackend::MergeDataAndStartSyncing(
     syncer::ModelType type,
     const syncer::SyncDataList& initial_sync_data,
     scoped_ptr<syncer::SyncChangeProcessor> sync_processor,
     scoped_ptr<syncer::SyncErrorFactory> sync_error_factory) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-  DCHECK(type == syncer::EXTENSION_SETTINGS ||
-         type == syncer::APP_SETTINGS);
-  DCHECK_EQ(sync_type_, syncer::UNSPECIFIED);
+  DCHECK_EQ(sync_type_, type);
   DCHECK(!sync_processor_.get());
   DCHECK(sync_processor.get());
   DCHECK(sync_error_factory.get());
 
-  sync_type_ = type;
   sync_processor_ = sync_processor.Pass();
   sync_error_factory_ = sync_error_factory.Pass();
 
   // Group the initial sync data by extension id.
   std::map<std::string, linked_ptr<DictionaryValue> > grouped_sync_data;
   for (syncer::SyncDataList::const_iterator it = initial_sync_data.begin();
       it != initial_sync_data.end(); ++it) {
     SettingSyncData data(*it);
     linked_ptr<DictionaryValue> sync_data =
         grouped_sync_data[data.extension_id()];
@@ skipping 64 matching lines @@
       storage->StopSyncing();
   }
 
   return syncer::SyncError();
 }
 
 void SettingsBackend::StopSyncing(syncer::ModelType type) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   DCHECK(type == syncer::EXTENSION_SETTINGS ||
          type == syncer::APP_SETTINGS);
-  DCHECK(sync_type_ == type || sync_type_ == syncer::UNSPECIFIED);
+  DCHECK_EQ(sync_type_, type);
 
   for (StorageObjMap::iterator it = storage_objs_.begin();
       it != storage_objs_.end(); ++it) {
     // Some storage areas may have already stopped syncing if they had areas
     // and syncing was disabled, but StopSyncing is safe to call multiple times.
     it->second->StopSyncing();
   }
 
-  sync_type_ = syncer::UNSPECIFIED;
   sync_processor_.reset();
   sync_error_factory_.reset();
 }
 
 scoped_ptr<SettingsSyncProcessor> SettingsBackend::CreateSettingsSyncProcessor(
     const std::string& extension_id) const {
   CHECK(sync_processor_.get());
   return scoped_ptr<SettingsSyncProcessor>(
       new SettingsSyncProcessor(extension_id,
                                 sync_type_,
                                 sync_processor_.get()));
 }
 
 }  // namespace extensions