[Device Service] Move Gamepad Blink headers to be part of the Gamepad client library

device/gamepad/public/cpp/gamepads.h

+// Copyright 2017 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_PUBLIC_CPP_GAMEPADS_H_
+#define DEVICE_GAMEPAD_PUBLIC_CPP_GAMEPADS_H_
+
+#include "device/gamepad/public/cpp/gamepad.h"
+
+namespace device {
+
+#pragma pack(push, 4)
+
+// This structure is intentionally POD and fixed size so that it can be stored
+// in shared memory between hardware polling threads and the rest of the
+// browser.
+class Gamepads {
+ public:
+  static const size_t kItemsLengthCap = 4;

[dcheng, 2017/04/12 23:33:27]

Nit: constexpr

[juncai, 2017/04/13 23:55:52]

Done.

+
+  // Gamepad data for N separate gamepad devices.
+  Gamepad items[kItemsLengthCap];
+};
+
+#pragma pack(pop)
+
+}  // namespace device
+
+#endif  // DEVICE_GAMEPAD_PUBLIC_CPP_GAMEPADS_H_