Expose Gamepad API instance for Cardboard button

device/gamepad/gamepad_pad_state_provider.h

 // 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.
 
 #ifndef DEVICE_GAMEPAD_GAMEPAD_PAD_STATE_PROVIDER_H_
 #define DEVICE_GAMEPAD_GAMEPAD_PAD_STATE_PROVIDER_H_
 
 #include <stdint.h>
 
 #include <limits>
 #include <memory>
 
 #include "device/gamepad/gamepad_export.h"
 #include "device/gamepad/gamepad_standard_mappings.h"
 #include "device/gamepad/public/cpp/gamepad.h"
 
 namespace device {
 
 class GamepadDataFetcher;
 
 enum GamepadSource {
   GAMEPAD_SOURCE_NONE = 0,
   GAMEPAD_SOURCE_ANDROID,
   GAMEPAD_SOURCE_GVR,
+  GAMEPAD_SOURCE_CARDBOARD,
   GAMEPAD_SOURCE_LINUX_UDEV,
   GAMEPAD_SOURCE_MAC_GC,
   GAMEPAD_SOURCE_MAC_HID,
   GAMEPAD_SOURCE_MAC_XBOX,
   GAMEPAD_SOURCE_OPENVR,
   GAMEPAD_SOURCE_TEST,
   GAMEPAD_SOURCE_WIN_XINPUT,
   GAMEPAD_SOURCE_WIN_RAW,
 };
 
@@ skipping 56 matching lines @@
                                  Gamepad* pad,
                                  bool sanitize);
 
   // Tracks the state of each gamepad slot.
   std::unique_ptr<PadState[]> pad_states_;
 };
 
 }  // namespace device
 
 #endif  // DEVICE_GAMEPAD_GAMEPAD_PAD_STATE_PROVIDER_H_