Extract colors from wallpaper and dynamically update login screen overlay

components/wallpaper/wallpaper_manager_base.h

 // Copyright 2014 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 COMPONENTS_WALLPAPER_WALLPAPER_MANAGER_BASE_H_
 #define COMPONENTS_WALLPAPER_WALLPAPER_MANAGER_BASE_H_
 
 #include <stddef.h>
 
 #include <deque>
@@ skipping 176 matching lines @@
 
    private:
     WallpaperManagerBase* wallpaper_manager_;  // not owned
 
     DISALLOW_COPY_AND_ASSIGN(TestApi);
   };
 
   class Observer {
    public:
     virtual ~Observer() {}
+    // Notified when the wallpaper animation finishes.
     virtual void OnWallpaperAnimationFinished(const AccountId& account_id) = 0;
+    // Notified when the wallpaper is updated and the color calculation results
+    // change.
+    virtual void OnWallpaperColorsChanged() {}
+    // Notified when the wallpaper is updated.
     virtual void OnUpdateWallpaperForTesting() {}
+    // Notified when the wallpaper pending list is empty.
     virtual void OnPendingListEmptyForTesting() {}
   };
 
   // set path IDs for used directories
   static void SetPathIds(int dir_user_data_enum,
                          int dir_chromeos_wallpapers_enum,
                          int dir_chromeos_custom_wallpapers_enum);
 
   // Returns custom wallpaper directory by appending corresponding |sub_dir|.
   static base::FilePath GetCustomWallpaperDir(const char* sub_dir);
@@ skipping 422 matching lines @@
   std::unique_ptr<user_manager::UserImage> default_wallpaper_image_;
 
   base::WeakPtrFactory<WallpaperManagerBase> weak_factory_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(WallpaperManagerBase);
 };
 
 }  // namespace wallpaper
 
-#endif  // COMPONENTS_WALLPAPER_WALLPAPER_MANAGER_BASE_H_
+#endif  // COMPONENTS_WALLPAPER_WALLPAPER_MANAGER_BASE_H_