sync: fix the way extension/app settings trigger deferred sync init

chrome/browser/extensions/api/storage/syncable_settings_storage.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/syncable_settings_storage.h"
 
 #include "base/strings/stringprintf.h"
 #include "chrome/browser/extensions/api/storage/settings_namespace.h"
 #include "chrome/browser/extensions/api/storage/settings_sync_processor.h"
 #include "chrome/browser/extensions/api/storage/settings_sync_util.h"
 #include "content/public/browser/browser_thread.h"
 #include "sync/api/sync_data.h"
 #include "sync/protocol/extension_setting_specifics.pb.h"
 
 namespace extensions {
 
 using content::BrowserThread;
 
 SyncableSettingsStorage::SyncableSettingsStorage(
     const scoped_refptr<ObserverListThreadSafe<SettingsObserver> >&
         observers,
     const std::string& extension_id,
-    ValueStore* delegate)
+    ValueStore* delegate,
+    syncer::ModelType sync_type,
+    const syncer::SyncableService::StartSyncFlare& flare)
     : observers_(observers),
       extension_id_(extension_id),
-      delegate_(delegate) {
+      delegate_(delegate),
+      sync_type_(sync_type),
+      flare_(flare) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
 }
 
 SyncableSettingsStorage::~SyncableSettingsStorage() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
 }
 
 size_t SyncableSettingsStorage::GetBytesInUse(const std::string& key) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   return delegate_->GetBytesInUse(key);
@@ skipping 76 matching lines @@
   WriteResult result = delegate_->Clear();
   if (result->HasError()) {
     return result.Pass();
   }
   SyncResultIfEnabled(result);
   return result.Pass();
 }
 
 void SyncableSettingsStorage::SyncResultIfEnabled(
     const ValueStore::WriteResult& result) {
-  if (sync_processor_.get() && !result->changes().empty()) {
+  if (result->changes().empty())
+    return;
+
+  if (sync_processor_.get()) {
     syncer::SyncError error = sync_processor_->SendChanges(result->changes());
     if (error.IsSet())
       StopSyncing();
+  } else {
+    // Tell sync to try and start soon, because syncable changes to sync_type_
+    // have started happening. This will cause sync to call us back
+    // asynchronously via StartSyncing(...) as soon as possible.
+    flare_.Run(sync_type_);

[not at google - send to devlin, 2014/01/15 18:39:46]

and it's ok to ignore the changes here because one it actually calls
StartSyncing the diff will be picked up. cool.

   }
 }
 
 // Sync-related methods.
 
 syncer::SyncError SyncableSettingsStorage::StartSyncing(
     const base::DictionaryValue& sync_state,
     scoped_ptr<SettingsSyncProcessor> sync_processor) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   DCHECK(!sync_processor_.get());
@@ skipping 245 matching lines @@
         syncer::SyncError::DATATYPE_ERROR,
         base::StringPrintf("Error pushing sync remove to local settings: %s",
             result->error().message.c_str()),
         sync_processor_->type());
   }
   changes->push_back(ValueStoreChange(key, old_value, NULL));
   return syncer::SyncError();
 }
 
 }  // namespace extensions