Factor Google Now welcome notifications out of DesktopNotificationService.

chrome/browser/notifications/google_now_notification_stats_collector.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/notifications/google_now_notification_stats_collector.h"
 
 #include <string>
 
 #include "base/metrics/sparse_histogram.h"
 #include "chrome/browser/browser_process.h"
+#include "chrome/browser/notifications/extension_welcome_notification.h"
 #include "chrome/browser/notifications/notification.h"
 #include "chrome/browser/notifications/notification_ui_manager.h"
 #include "content/public/browser/user_metrics.h"
 #include "ui/message_center/notification.h"
 
 namespace {
-const char kChromeNowExtensionID[] = "pafkbggdmjlpgkdkcbjmhmfcdpncadgh";
 const int kNotificationsMaxCount = 20;
 }
 
 GoogleNowNotificationStatsCollector::GoogleNowNotificationStatsCollector(
     message_center::MessageCenter* message_center)
     : message_center_(message_center) {
   message_center_->AddObserver(this);
 }
 
 GoogleNowNotificationStatsCollector::~GoogleNowNotificationStatsCollector() {
@@ skipping 22 matching lines @@
 
 bool GoogleNowNotificationStatsCollector::IsNotificationIdForGoogleNow(
   const std::string& notification_id) {
   bool isGoogleNowNotification = false;
   const Notification* const notification =
       g_browser_process->notification_ui_manager()->FindById(notification_id);
   if (notification) {
     isGoogleNowNotification =
         ((notification->notifier_id().type ==
               message_center::NotifierId::APPLICATION) &&
-        (notification->notifier_id().id == kChromeNowExtensionID));
+        (notification->notifier_id().id ==
+              ExtensionWelcomeNotification::kChromeNowExtensionID));
   }
   return isGoogleNowNotification;
 }
 
 int GoogleNowNotificationStatsCollector::CountVisibleGoogleNowNotifications() {
   typedef message_center::NotificationList::Notifications Notifications;
   const Notifications visible_notifications =
       message_center_->GetVisibleNotifications();
   int google_now_notification_count = 0;
   for (Notifications::iterator iter = visible_notifications.begin();
       iter != visible_notifications.end();
       ++iter) {
-    if ((*iter)->notifier_id().id == kChromeNowExtensionID)
+    if ((*iter)->notifier_id().id ==
+            ExtensionWelcomeNotification::kChromeNowExtensionID)
       google_now_notification_count++;
   }
   return google_now_notification_count;
 }