Enable extensions sync by default.

chrome/browser/sync/profile_sync_factory_impl.cc

 // Copyright (c) 2010 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 "base/logging.h"
 #include "chrome/browser/defaults.h"
 #include "chrome/browser/profile.h"
 #include "chrome/browser/sync/glue/autofill_change_processor.h"
 #include "chrome/browser/sync/glue/autofill_data_type_controller.h"
@@ skipping 67 matching lines @@
         new AutofillDataTypeController(this, profile_, pss));
   }
 
   // Bookmark sync is enabled by default.  Register unless explicitly
   // disabled.
   if (!command_line_->HasSwitch(switches::kDisableSyncBookmarks)) {
     pss->RegisterDataTypeController(
         new BookmarkDataTypeController(this, profile_, pss));
   }
 
-  // Extension sync is disabled by default.  Register only if
-  // explicitly enabled.
-  if (command_line_->HasSwitch(switches::kEnableSyncExtensions)) {
+  // Extension sync is enabled by default.  Register unless explicitly
+  // disabled.
+  if (!command_line_->HasSwitch(switches::kDisableSyncExtensions)) {
     pss->RegisterDataTypeController(
         new ExtensionDataTypeController(this, profile_, pss));
   }
 
   // Password sync is disabled by default.  Register only if
   // explicitly enabled.
   if (command_line_->HasSwitch(switches::kEnableSyncPasswords)) {
     pss->RegisterDataTypeController(
         new PasswordDataTypeController(this, profile_, pss));
   }
@@ skipping 114 matching lines @@
     browser_sync::UnrecoverableErrorHandler* error_handler) {
   TypedUrlModelAssociator* model_associator =
       new TypedUrlModelAssociator(profile_sync_service,
                                   history_backend);
   TypedUrlChangeProcessor* change_processor =
       new TypedUrlChangeProcessor(model_associator,
                                   history_backend,
                                   error_handler);
   return SyncComponents(model_associator, change_processor);
 }