cheets: implement cros side of WallpaperManagerService.

components/arc/common/wallpaper.mojom

+// 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.
+//
+// Next MinVersion: 2
+
+module arc.mojom;
+
+// Handles wallpaper calls from ARC in Chrome.
+// Next method ID:3
+interface WallpaperHost {
+  // Gets current wallpaper and send it back to ARC.
+  [MinVersion=1] GetWallpaper@2() => (array<uint8> wallpaper);

[hidehiko, 2016/08/22 02:30:11]

@1

Could you explicitly document the encoding of the |wallpaper|'s content?

[Muyuan, 2016/08/22 22:25:00]

Done.

+
+  // Sets an image from ARC as the wallpaper.
+  // |jpeg_data| is a JPEG encoded wallpaper image.
+  [MinVersion=1] SetWallpaper@1(array<uint8> jpeg_data);

[hidehiko, 2016/08/22 02:30:10]

@0

[Muyuan, 2016/08/22 22:25:00]

Done.

+};
+
+// Connects with container side to publish wallpaper related intents.
+// Next method ID:2
+interface WallpaperInstance {
+   // Establishes communication with the container side.

[hidehiko, 2016/08/22 02:30:11]

nit: 2-indent please.

[Muyuan, 2016/08/22 22:25:00]

Done.

+   Init@1(WallpaperHost host_ptr);

[Luis Héctor Chávez, 2016/08/19 23:22:56]

nit: Init@0

[Muyuan, 2016/08/22 22:25:00]

Done.

+};