Use DCHECKs when observing only a single notification.

chrome/browser/web_applications/update_shortcut_worker_win.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/web_applications/update_shortcut_worker_win.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 
@@ skipping 47 matching lines @@
 
 void UpdateShortcutWorker::Run() {
   // Starting by downloading app icon.
   DownloadIcon();
 }
 
 void UpdateShortcutWorker::Observe(
     int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_TAB_CLOSING &&
-      content::Source<NavigationController>(source).ptr() ==
-        &web_contents_->GetController()) {
+  DCHECK_EQ(chrome::NOTIFICATION_TAB_CLOSING, type);
+
+  if (content::Source<NavigationController>(source).ptr() ==
+      &web_contents_->GetController()) {
     // Underlying tab is closing.
-    web_contents_ = NULL;
+    web_contents_ = nullptr;
   }
 }
 
 void UpdateShortcutWorker::DownloadIcon() {
   // FetchIcon must run on UI thread because it relies on WebContents
   // to download the icon.
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   if (web_contents_ == NULL) {
     DeleteMe();  // We are done if underlying WebContents is gone.
@@ skipping 159 matching lines @@
                  base::Unretained(this)));
   }
 }
 
 void UpdateShortcutWorker::DeleteMeOnUIThread() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   delete this;
 }
 
 }  // namespace web_app