[Extensions] Apply WARN_UNUSED_RESULT and final keyword to ExtensionFunctions.

extensions/browser/api/networking_config/networking_config_api.cc

 // Copyright 2015 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 <string>
 
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "extensions/browser/api/networking_config/networking_config_api.h"
 #include "extensions/browser/api/networking_config/networking_config_service.h"
@@ skipping 71 matching lines @@
   EXTENSION_FUNCTION_VALIDATE(parameters_.get());
 
   NetworkingConfigService* service =
       NetworkingConfigServiceFactory::GetForBrowserContext(browser_context());
   DCHECK(service);
 
   const NetworkingConfigService::AuthenticationResult& last_result =
       service->GetAuthenticationResult();
   if (last_result.authentication_state != NetworkingConfigService::NOTRY ||
       last_result.guid != parameters_->guid) {
-    RespondNow(Error(kAuthenticationResultFailed));
+    return RespondNow(Error(kAuthenticationResultFailed));
   }
 
   // Populate NetworkingCaptivePortalAPI::AuthenticationResult.
   NetworkingConfigService::AuthenticationResult authentication_result = {
       extension_id(), parameters_->guid, NetworkingConfigService::FAILED,
   };
   switch (parameters_->result) {
     case core_api::networking_config::AUTHENTICATION_RESULT_NONE:
       NOTREACHED();
       break;
@@ skipping 16 matching lines @@
   }
   service->SetAuthenticationResult(authentication_result);
   return RespondNow(NoArguments());
 }
 
 NetworkingConfigFinishAuthenticationFunction::
     ~NetworkingConfigFinishAuthenticationFunction() {
 }
 
 }  // namespace extensions