Update the PushEvent to have a nullable PushMessageData

chrome/browser/push_messaging/push_messaging_service_impl.cc

 // Copyright 2014 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/push_messaging/push_messaging_service_impl.h"
 
 #include <vector>
 
 #include "base/barrier_closure.h"
 #include "base/bind.h"
@@ skipping 199 matching lines @@
                            app_identifier.service_worker_registration_id(),
                            message, message_handled_closure,
                            content::PUSH_DELIVERY_STATUS_PERMISSION_DENIED);
     return;
   }
 
   rappor::SampleDomainAndRegistryFromGURL(
       g_browser_process->rappor_service(),
       "PushMessaging.MessageReceived.Origin", app_identifier.origin());
 
-  std::string data;
-  if (AreMessagePayloadsEnabled() && message.decrypted)
-    data = message.raw_data;
+  // The payload of a push message can be valid with content, valid with empty
+  // content, or null. Only set the payload data if it is non-null.
+  content::PushEventPayload payload;
+  if (AreMessagePayloadsEnabled() && message.decrypted) {
+    payload.setData(message.raw_data);

[Peter Beverloo, 2016/01/25 17:39:06]

nit: we don't use curly brackets for one-line conditionals in C++ (we do in
Java).

[harkness, 2016/01/26 12:07:19]

Done.

+  }
 
   // Dispatch the message to the appropriate Service Worker.
   content::BrowserContext::DeliverPushMessage(
       profile_, app_identifier.origin(),
-      app_identifier.service_worker_registration_id(), data,
+      app_identifier.service_worker_registration_id(), payload,
       base::Bind(&PushMessagingServiceImpl::DeliverMessageCallback,
                  weak_factory_.GetWeakPtr(), app_identifier.app_id(),
                  app_identifier.origin(),
                  app_identifier.service_worker_registration_id(), message,
                  message_handled_closure));
 
   // Inform tests observing message dispatching about the event.
   if (!message_dispatched_callback_for_testing_.is_null()) {
     message_dispatched_callback_for_testing_.Run(
         app_id, app_identifier.origin(),
-        app_identifier.service_worker_registration_id(), data);
+        app_identifier.service_worker_registration_id(), payload);
   }
 }
 
 void PushMessagingServiceImpl::DeliverMessageCallback(
     const std::string& app_id,
     const GURL& requesting_origin,
     int64_t service_worker_registration_id,
     const gcm::IncomingMessage& message,
     const base::Closure& message_handled_closure,
     content::PushDeliveryStatus status) {
@@ skipping 522 matching lines @@
       switches::kEnableExperimentalWebPlatformFeatures);
 }
 
 gcm::GCMDriver* PushMessagingServiceImpl::GetGCMDriver() const {
   gcm::GCMProfileService* gcm_profile_service =
       gcm::GCMProfileServiceFactory::GetForProfile(profile_);
   CHECK(gcm_profile_service);
   CHECK(gcm_profile_service->driver());
   return gcm_profile_service->driver();
 }