-Add a mojo service to get video frames from the camera through an android service

mojo/services/camera_roll/public/interfaces/camera_roll.mojom

-// Copyright 2015 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.
-
-[DartPackage="mojo_services"]
-module mojo;
-
-struct Photo {
-  // A string to uniquely identify an instance of a |Photo|. This can be used
-  // to de-duplicate photos over multiple runs on the camera roll.
-  string unique_id;
-
-  // Stream to read contents of the photo from.
-  handle<data_pipe_consumer> content;
-};
-
-// |CameraRollService| provides access to the device's camera roll.
-// The camera roll is exposed as a snapshot of all photos available as a list.
-// The head of the list (element with index 0) is a photo with the latest
-// timestamp and subsequent elements are in decreasing order of timestamp.
-interface CameraRollService {
-  // Updates the snapshot of all photos available. Photos might have been added
-  // or removed after the service was started or |Update| was called.
-  Update();
-  // Get the number of photos available in the current snapshot.
-  GetCount() => (uint32 num_photos);
-  // Get the photo from the current snapshot at |index|. null will be returned
-  // if such an index is out-of-bounds.
-  GetPhoto(uint32 index) => (Photo? photo);
-};