Improve grammar in some comments.

ui/message_center/views/message_popup_collection.h

 // Copyright (c) 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.
 
 #ifndef UI_MESSAGE_CENTER_VIEWS_MESSAGE_POPUP_COLLECTION_H_
 #define UI_MESSAGE_CENTER_VIEWS_MESSAGE_POPUP_COLLECTION_H_
 
 #include <stddef.h>
 
 #include <list>
@@ skipping 59 matching lines @@
   void ClickOnSettingsButton(const std::string& notification_id) override;
 
   void MarkAllPopupsShown();
 
   // Since these events are really coming from individual toast widgets,
   // it helps to be able to keep track of the sender.
   void OnMouseEntered(ToastContentsView* toast_entered);
   void OnMouseExited(ToastContentsView* toast_exited);
 
   // Invoked by toasts when they start/finish their animations.
-  // While "defer counter" is greater then zero, the popup collection does
+  // While "defer counter" is greater than zero, the popup collection does
   // not perform updates. It is used to wait for various animations and user
   // actions like serial closing of the toasts, when the remaining toasts "flow
   // under the mouse".
   void IncrementDeferCounter();
   void DecrementDeferCounter();
 
   // Runs the next step in update/animate sequence, if the defer counter is not
   // zero. Otherwise, simply waits when it becomes zero.
   void DoUpdateIfPossible();
 
@@ skipping 81 matching lines @@
   // Gives out weak pointers to toast contents views which have an unrelated
   // lifetime.  Must remain the last member variable.
   base::WeakPtrFactory<MessagePopupCollection> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MessagePopupCollection);
 };
 
 }  // namespace message_center
 
 #endif  // UI_MESSAGE_CENTER_VIEWS_MESSAGE_POPUP_COLLECTION_H_