Add random motion input to keyboard

src/input_common/motion_from_button.h

@@ -0,0 +1,25 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "core/frontend/input.h"
+
+namespace InputCommon {
+
+/**
+ * An motion device factory that takes a keyboard button and uses it as a random
+ * motion device.
+ */
+class MotionFromButton final : public Input::Factory<Input::MotionDevice> {
+public:
+    /**
+     * Creates an motion device from button devices
+     * @param params contains parameters for creating the device:
+     *     - "key": a serialized ParamPackage for creating a button device
+     */
+    std::unique_ptr<Input::MotionDevice> Create(const Common::ParamPackage& params) override;
+};
+
+} // namespace InputCommon