Use DCHECKs when observing only a single notification.

chrome/browser/chromeos/first_run/drive_first_run_controller.cc

 // Copyright 2013 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/chromeos/first_run/drive_first_run_controller.h"
 
 #include <stdint.h>
 #include <utility>
 
 #include "ash/common/system/tray/system_tray_delegate.h"
@@ skipping 310 matching lines @@
       std::string());
 
   // Return false as we already created the WebContents here.
   return false;
 }
 
 void DriveWebContentsManager::Observe(
     int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_BACKGROUND_CONTENTS_OPENED) {
-    const std::string app_id = base::UTF16ToUTF8(
-        content::Details<BackgroundContentsOpenedDetails>(details)
-            ->application_id);
-    if (app_id == app_id_)
-      OnOfflineInit(true, DriveFirstRunController::OUTCOME_OFFLINE_ENABLED);
-  }
+  DCHECK_EQ(chrome::NOTIFICATION_BACKGROUND_CONTENTS_OPENED, type);
+  const std::string app_id = base::UTF16ToUTF8(
+      content::Details<BackgroundContentsOpenedDetails>(details)
+          ->application_id);
+  if (app_id == app_id_)
+    OnOfflineInit(true, DriveFirstRunController::OUTCOME_OFFLINE_ENABLED);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // DriveFirstRunController
 
 DriveFirstRunController::DriveFirstRunController(Profile* profile)
     : profile_(profile),
       started_(false),
       initial_delay_secs_(kInitialDelaySeconds),
       web_contents_timeout_secs_(kWebContentsTimeoutSeconds),
@@ skipping 120 matching lines @@
           base::UTF8ToUTF16(extension->name()), GURL(),
           message_center::NotifierId(message_center::NotifierId::APPLICATION,
                                      kDriveHostedAppId),
           data, new DriveOfflineNotificationDelegate(profile_)));
   notification->set_priority(message_center::LOW_PRIORITY);
   message_center::MessageCenter::Get()->AddNotification(
       std::move(notification));
 }
 
 }  // namespace chromeos