Fix TryToCloseBrowserList not checking for null callbacks

chrome/browser/ui/browser_list.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_BROWSER_LIST_H_
 #define CHROME_BROWSER_UI_BROWSER_LIST_H_
 
 #include <stddef.h>
 
 #include <vector>
@@ skipping 74 matching lines @@
   // Notifies the observers when browser close was started. This may be called
   // more than once for a particular browser.
   static void NotifyBrowserCloseStarted(Browser* browser);
 
   // Closes all browsers for |profile| across all desktops.
   // TODO(mlerman): Move the Profile Deletion flow to use the overloaded
   // version of this method with a callback, then remove this method.
   static void CloseAllBrowsersWithProfile(Profile* profile);
 
   // Closes all browsers for |profile| across all desktops. Uses
-  // TryToCloseBrowserList() to do the actual closing. Trigger any
-  // OnBeforeUnload events if |if_force| is false. If all OnBeforeUnload events
-  // are confirmed or |skip_beforeunload| is true, |on_close_success| is called,
-  // otherwise |on_close_aborted| is called.
-  // Note that if there is any browser window has been used before, user
-  // should always has a chance to save his or her work before closing windows
-  // without trigger beforeunload event.
+  // TryToCloseBrowserList() to do the actual closing. Triggers any
+  // OnBeforeUnload events unless |skip_beforeunload| is true. If all
+  // OnBeforeUnload events are confirmed or |skip_beforeunload| is true,
+  // |on_close_success| is called, otherwise |on_close_aborted| is called. Both
+  // callbacks may be null.
+  // Note that if there is any browser window that has been used before, the
+  // user should always have a chance to save their work before closing windows
+  // without triggering beforeunload events.
   static void CloseAllBrowsersWithProfile(Profile* profile,
                                           const CloseCallback& on_close_success,
                                           const CloseCallback& on_close_aborted,
                                           bool skip_beforeunload);
 
   // Returns true if at least one incognito session is active across all
   // desktops.
   static bool IsIncognitoSessionActive();
 
   // Returns true if at least one incognito session is active for |profile|
@@ skipping 45 matching lines @@
   // removal across all BrowserLists.
   static base::LazyInstance<
       base::ObserverList<chrome::BrowserListObserver>>::Leaky observers_;
 
   static BrowserList* instance_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserList);
 };
 
 #endif  // CHROME_BROWSER_UI_BROWSER_LIST_H_