Mark create/update/clear callbacks of notification API as optional

chrome/browser/extensions/api/notifications/notifications_api.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/notifications/notifications_api.h"
 
 #include "base/callback.h"
 #include "base/guid.h"
 #include "base/rand_util.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 459 matching lines @@
 
 NotificationsCreateFunction::~NotificationsCreateFunction() {
 }
 
 bool NotificationsCreateFunction::RunNotificationsApi() {
   params_ = api::notifications::Create::Params::Create(*args_);
   EXTENSION_FUNCTION_VALIDATE(params_.get());
 
   const std::string extension_id(extension_->id());
   std::string notification_id;
-  if (!params_->notification_id.empty()) {
+  if (params_->notification_id.get() && !params_->notification_id->empty()) {
     // If the caller provided a notificationId, use that.
-    notification_id = params_->notification_id;
+    notification_id = *params_->notification_id;
   } else {
     // Otherwise, use a randomly created GUID. In case that GenerateGUID returns
     // the empty string, simply generate a random string.
     notification_id = base::GenerateGUID();
     if (notification_id.empty())
       notification_id = base::RandBytesAsString(16);
   }
 
   SetResult(new base::StringValue(notification_id));
 
@@ skipping 108 matching lines @@
           ? api::notifications::PERMISSION_LEVEL_GRANTED
           : api::notifications::PERMISSION_LEVEL_DENIED;
 
   SetResult(new base::StringValue(api::notifications::ToString(result)));
   SendResponse(true);
 
   return true;
 }
 
 }  // namespace extensions