Convert Gamepad IPC messages into mojo interface.

device/gamepad/public/interfaces/gamepad.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.
 
 module device.mojom;
 
 struct GamepadQuaternion {
   float x;
   float y;
   float z;
@@ skipping 31 matching lines @@
   bool connected;
   array<uint16> id;
   uint64 timestamp;
   array<double> axes;
   array<GamepadButton> buttons;
   array<uint16> mapping;
   GamepadPose? pose;
   GamepadHand hand;
   uint32 display_id;
 };
+
+interface GamepadObserver {
+  GamepadConnected(int32 index, Gamepad gamepad);
+  GamepadDisconnected(int32 index, Gamepad gamepad);
+};
+
+// Asks the browser process to start polling, and return a shared memory
+// handles that will hold the data from the hardware. See
+// gamepad_hardware_buffer.h for a description of how synchronization is
+// handled. The number of Starts should match the number of Stops.
+interface GamepadMonitor {
+  [Sync]
+  GamepadStartPolling() => (handle<shared_buffer> memory_handle);
+  GamepadStopPolling();

[blundell, 2016/12/01 16:01:26]

Did you reason about whether this one should be sync as well (as it was in the
old impl)?

[ke.he, 2016/12/02 13:20:47]

It should be Sync as it was in the old impl. Thanks!
done.

+  SetObserver(GamepadObserver gamepad_observer);
+};