Convert device_sensors to use mojo.

device/sensors/public/interfaces/motion.mojom

Index: device/sensors/public/interfaces/motion.mojom
diff --git a/device/sensors/public/interfaces/motion.mojom b/device/sensors/public/interfaces/motion.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..7755344fdae3a462231db1eac44782591eacabdf
--- /dev/null
+++ b/device/sensors/public/interfaces/motion.mojom
@@ -0,0 +1,10 @@
+// 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.
+
+module device.mojom;
+
+interface MotionSensor {
+  StartPolling() => (handle<shared_buffer> memory_handle);
+  StopPolling();
+};