ash: Add support for additional icons in apps search list.

ui/app_list/search_result_observer.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 UI_APP_LIST_SEARCH_RESULT_OBSERVER_H_
 #define UI_APP_LIST_SEARCH_RESULT_OBSERVER_H_
 
 #include "ui/app_list/app_list_export.h"
 
 namespace app_list {
 
 class APP_LIST_EXPORT SearchResultObserver {
  public:
-  // Invoked when SearchResult icon has changed.
+  // Invoked when the SearchResult's icon has changed.
   virtual void OnIconChanged() = 0;
 
+  // Invoked when the SearchResult's action icons have been changed.
+  virtual void OnActionIconsChanged() = 0;
+
  protected:
   virtual ~SearchResultObserver() {}
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_SEARCH_RESULT_OBSERVER_H_