patch from issue 2577273002 at patchset 20001 (http://crrev.com/2577273002#ps20001)

chrome/browser/icon_manager.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.
 //
 // Class for finding and caching Windows explorer icons. The IconManager
 // lives on the UI thread but performs icon extraction work on the file thread
 // to avoid blocking the UI thread with potentially expensive COM and disk
 // operations.
 //
 // Terminology
@@ skipping 36 matching lines @@
 
 #include <map>
 #include <memory>
 
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/task/cancelable_task_tracker.h"
 #include "chrome/browser/icon_loader.h"
 #include "ui/gfx/image/image.h"
 
-class IconManager : public IconLoader::Delegate {
+class IconManager {
  public:
   IconManager();
-  ~IconManager() override;
+  ~IconManager();
 
   // Synchronous call to examine the internal caches for the icon. Returns the
   // icon if we have already loaded it, or null if we don't have it and must
   // load it via LoadIcon(). The returned bitmap is owned by the IconManager and
   // must not be free'd by the caller. If the caller needs to modify the icon,
   // it must make a copy and modify the copy.
   gfx::Image* LookupIconFromFilepath(const base::FilePath& file_path,
                                      IconLoader::IconSize size);
 
-  using IconRequestCallback = base::Callback<void(gfx::Image*)>;
+  using IconRequestCallback = base::OnceCallback<void(gfx::Image*)>;
 
   // Asynchronous call to lookup and return the icon associated with file. The
   // work is done on the file thread, with the callbacks running on the thread
   // this function is called.
   //
   // Note:
   // 1. This does *not* check the cache.
   // 2. The returned bitmap pointer is *not* owned by callback. So callback
   //    should never keep it or delete it.
   // 3. The gfx::Image pointer passed to the callback will be null if decoding
   //    failed.
   base::CancelableTaskTracker::TaskId LoadIcon(
       const base::FilePath& file_name,
       IconLoader::IconSize size,
-      const IconRequestCallback& callback,
+      IconRequestCallback callback,
       base::CancelableTaskTracker* tracker);
 
  private:
-  // IconLoader::Delegate interface.
-  void OnImageLoaded(IconLoader* loader,
-                     std::unique_ptr<gfx::Image> result,
-                     const IconLoader::IconGroup& group) override;
+  void OnIconLoaded(IconLoader* loader,
+                    std::unique_ptr<gfx::Image> result,
+                    const IconLoader::IconGroup& group);
 
   struct CacheKey {
     CacheKey(const IconLoader::IconGroup& group, IconLoader::IconSize size);
 
     // Used as a key in the map below, so we need this comparator.
     bool operator<(const CacheKey &other) const;
 
     IconLoader::IconGroup group;
     IconLoader::IconSize size;
   };
 
   std::map<base::FilePath, IconLoader::IconGroup> group_cache_;
   std::map<CacheKey, std::unique_ptr<gfx::Image>> icon_cache_;
 
   // Asynchronous requests that have not yet been completed.
   struct ClientRequest;
   std::map<IconLoader*, ClientRequest> requests_;
 
   DISALLOW_COPY_AND_ASSIGN(IconManager);
 };
 
 #endif  // CHROME_BROWSER_ICON_MANAGER_H_