[ash-md] WIP Added wallpaper color caching.

components/wallpaper/wallpaper_color_cache.h

+// Copyright 2017 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_COLOR_CACHE_H_
+#define COMPONENTS_WALLPAPER_WALLPAPER_COLOR_CACHE_H_
+
+#include <stdint.h>
+
+#include "base/macros.h"
+#include "components/wallpaper/wallpaper_export.h"
+#include "third_party/skia/include/core/SkColor.h"
+
+namespace wallpaper {
+
+class WALLPAPER_EXPORT WallpaperColorCache {
+ public:
+  virtual ~WallpaperColorCache() {}
+
+  virtual bool GetColor(uint32_t image_id, SkColor* color) const = 0;
+  virtual void SetColor(uint32_t image_id, SkColor color) = 0;
+
+ protected:
+  WallpaperColorCache() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(WallpaperColorCache);
+};
+
+}  // namespace wallpaper
+
+#endif  // COMPONENTS_WALLPAPER_WALLPAPER_COLOR_CACHE_H_