Notifications: Retain button hover state during content updates.

ui/message_center/views/notification_button.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 "ui/message_center/views/notification_button.h"
 
 #include "ui/gfx/canvas.h"
 #include "ui/message_center/message_center_style.h"
 #include "ui/message_center/views/constants.h"
 #include "ui/views/background.h"
@@ skipping 80 matching lines @@
   // We render differently when focused.
   SchedulePaint();
  }
 
 void NotificationButton::OnBlur() {
   views::CustomButton::OnBlur();
   // We render differently when focused.
   SchedulePaint();
 }
 
+void NotificationButton::ViewHierarchyChanged(
+    const ViewHierarchyChangedDetails& details) {
+  // We disable view hierarchy change detection in the parent
+  // because it resets the hoverstate, which we do not want
+  // when we update the view to contain a new label or image.
+  views::View::ViewHierarchyChanged(details);
+}
+
 void NotificationButton::StateChanged() {
   if (state() == STATE_HOVERED || state() == STATE_PRESSED) {
     set_background(views::Background::CreateSolidBackground(
         message_center::kHoveredButtonBackgroundColor));
   } else {
     set_background(NULL);
   }
 }
 
 }  // namespace message_center