Enable -Wundeclared-selector on ios.

ios/chrome/browser/sync/sync_observer_bridge.mm

 // Copyright 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 "ios/chrome/browser/sync/sync_observer_bridge.h"
 
 #include "base/logging.h"
 #include "components/sync/driver/sync_service.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 SyncObserverBridge::SyncObserverBridge(id<SyncObserverModelBridge> delegate,
                                        syncer::SyncService* sync_service)
     : delegate_(delegate), scoped_observer_(this) {
   DCHECK(delegate);
   if (sync_service)
     scoped_observer_.Add(sync_service);
 }
 
 SyncObserverBridge::~SyncObserverBridge() {
 }
 
 void SyncObserverBridge::OnStateChanged() {
   [delegate_ onSyncStateChanged];
 }
 
 void SyncObserverBridge::OnSyncConfigurationCompleted() {
-  if ([delegate_ respondsToSelector:@selector(onSyncConfigurationCompleted:)])
+  if ([delegate_ respondsToSelector:@selector(onSyncConfigurationCompleted)])
     [delegate_ onSyncConfigurationCompleted];
 }