arc: IPC method to set custom wallpaper.

components/arc/set_wallpaper_delegate.h

+// Copyright 2016 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_ARC_SET_WALLPAPER_DELEGATE_H_
+#define COMPONENTS_ARC_SET_WALLPAPER_DELEGATE_H_
+
+#include <string>
+
+namespace arc {
+
+// Delegate to allow setting the wallpaper.
+class SetWallpaperDelegate {
+ public:
+  virtual ~SetWallpaperDelegate() = default;
+
+  // Sets an image represented in JPEG format as the wallpaper.
+  virtual void SetWallpaper(const std::string& jpeg_data) = 0;
+};
+
+}  // namespace arc
+
+#endif  // COMPONENTS_ARC_SET_WALLPAPER_DELEGATE_H_