[ash-md] WIP Added wallpaper color caching.

ash/common/wallpaper/wallpaper_controller.h

Index: ash/common/wallpaper/wallpaper_controller.h
diff --git a/ash/common/wallpaper/wallpaper_controller.h b/ash/common/wallpaper/wallpaper_controller.h
index 63244d6cd4f3708fa97663b60d7edd6d52157f8c..225436ead78d33a4c1645eb7eb5255a24724b040 100644
--- a/ash/common/wallpaper/wallpaper_controller.h
+++ b/ash/common/wallpaper/wallpaper_controller.h
@@ -21,12 +21,12 @@
 #include "mojo/public/cpp/bindings/binding_set.h"
 #include "ui/gfx/color_analysis.h"
 #include "ui/gfx/image/image_skia.h"
-
 namespace base {
 class TaskRunner;
 }
 
 namespace wallpaper {
+class WallpaperColorCache;
 class WallpaperColorCalculator;
 class WallpaperResizer;
 }
@@ -111,8 +111,12 @@ class ASH_EXPORT WallpaperController
   // Opens the set wallpaper page in the browser.
   void OpenSetWallpaperPage();
 
+  // TODO(bruthig) Document me.
+  void SetWallpaperColorCache(wallpaper::WallpaperColorCache* color_cache);
+
   // mojom::WallpaperController overrides:
   void SetWallpaperPicker(mojom::WallpaperPickerPtr picker) override;
+  // TODO(bruthig): Add an std::string |image_id| field.
   void SetWallpaper(const SkBitmap& wallpaper,
                     wallpaper::WallpaperLayout layout) override;
 
@@ -170,6 +174,9 @@ class ASH_EXPORT WallpaperController
   // Asynchronous task to extract colors from the wallpaper.
   std::unique_ptr<wallpaper::WallpaperColorCalculator> color_calculator_;
 
+  // TODO(bruthig) Document me.
+  wallpaper::WallpaperColorCache* color_cache_;
+
   // The prominent color extracted from the current wallpaper.
   // SK_ColorTRANSPARENT is used by default or if extracting colors fails.
   SkColor prominent_color_;