cheets: implement cros side of WallpaperManagerService.

components/arc/common/wallpaper.mojom

Index: components/arc/common/wallpaper.mojom
diff --git a/components/arc/common/wallpaper.mojom b/components/arc/common/wallpaper.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..6324f81f6ce20c4eab615711fd3eb5badcc29da2
--- /dev/null
+++ b/components/arc/common/wallpaper.mojom
@@ -0,0 +1,25 @@
+// 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:2
+interface WallpaperHost {
+  // Gets current wallpaper encoded in JPEG and send it back to ARC.
+  [MinVersion=1] GetWallpaper@1() => (array<uint8> wallpaper);

[Shuhei Takahashi, 2016/08/23 09:34:21]

I'm not sure about security implication of allowing ARC to read the current
wallpaper. Did you talk with security teams?

[Muyuan, 2016/08/23 19:45:49]

Acknowledged.

+
+  // Sets an image from ARC as the wallpaper.
+  // |jpeg_data| is a JPEG encoded wallpaper image.
+  [MinVersion=1] SetWallpaper@0(array<uint8> jpeg_data);

[Shuhei Takahashi, 2016/08/23 09:34:21]

Optional: You can just skip MinVersion since those APIs exist from the first
version.

[Muyuan, 2016/08/23 19:45:49]

Thx. Is it ok to keep it just to look consistent?

+};
+
+// Connects with container side to publish wallpaper related intents.
+// Next method ID:1
+interface WallpaperInstance {
+  // Establishes communication with the container side.
+  Init@0(WallpaperHost host_ptr);
+};