Enable tab sync on all platforms by default.

chrome/browser/sync/profile_sync_components_factory_impl.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 "base/command_line.h"
 #include "build/build_config.h"
 #include "chrome/browser/extensions/app_notification_manager.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/settings/settings_frontend.h"
 #include "chrome/browser/prefs/pref_model_associator.h"
@@ skipping 136 matching lines @@
         new TypedUrlDataTypeController(this, profile_, pss));
   }
 
   // Search Engine sync is enabled by default.  Register only if explicitly
   // disabled.
   if (!command_line_->HasSwitch(switches::kDisableSyncSearchEngines)) {
     pss->RegisterDataTypeController(
         new SearchEngineDataTypeController(this, profile_, pss));
   }
 
-  // Session sync is disabled by default, but has some logic to automatically
-  // enable.  Register only if explicitly enabled and not explicitly disabled.
-  if (command_line_->HasSwitch(switches::kEnableSyncTabs) &&
-      !command_line_->HasSwitch(switches::kDisableSyncTabs)) {
+  // Session sync is enabled by default.  Register unless explicitly disabled.
+  // TODO(dubroy): Once this change is permanent, clean up the logic for
+  // explicitly enabling tab sync (http://crbug.com/118570).
+  if (!command_line_->HasSwitch(switches::kDisableSyncTabs)) {
     pss->RegisterDataTypeController(
         new SessionDataTypeController(this, profile_, pss));
   }
 
   // Extension setting sync is enabled by default.  Register unless explicitly
   // disabled.
   if (!command_line_->HasSwitch(switches::kDisableSyncExtensionSettings)) {
     pss->RegisterDataTypeController(
         new ExtensionSettingDataTypeController(
             syncable::EXTENSION_SETTINGS, this, profile_, pss));
@@ skipping 157 matching lines @@
 ProfileSyncComponentsFactory::SyncComponents
     ProfileSyncComponentsFactoryImpl::CreateSessionSyncComponents(
        ProfileSyncService* profile_sync_service,
         DataTypeErrorHandler* error_handler) {
   SessionModelAssociator* model_associator =
       new SessionModelAssociator(profile_sync_service);
   SessionChangeProcessor* change_processor =
       new SessionChangeProcessor(error_handler, model_associator);
   return SyncComponents(model_associator, change_processor);
 }