ozone: evdev: Add gamepad support

ui/events/ozone/gamepad/gamepad_mapping.h

Index: ui/events/ozone/gamepad/gamepad_mapping.h
diff --git a/ui/events/ozone/gamepad/gamepad_mapping.h b/ui/events/ozone/gamepad/gamepad_mapping.h
new file mode 100644
index 0000000000000000000000000000000000000000..e864e977e7ae4ff3ece2242e9d9a7749b21a6de3
--- /dev/null
+++ b/ui/events/ozone/gamepad/gamepad_mapping.h
@@ -0,0 +1,28 @@
+// 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 UI_EVENTS_OZONE_GAMEPAD_GAMEPAD_MAPPING_H_
+#define UI_EVENTS_OZONE_GAMEPAD_GAMEPAD_MAPPING_H_
+
+#include "ui/events/ozone/gamepad/webgamepad_constants.h"
+
+namespace ui {
+
+// The following HATX and HATY is not part of web gamepad definition, but we
+// need to specially treat them cause HAT_Y can be mapped to DPAD_UP or
+// DPAD_DOWN, and HAT_X can be mapped to DAPD_LEFT or DPAD_RIGHT.
+constexpr int kHAT_X = 4;
+constexpr int kHAT_Y = 5;
+
+typedef bool (*GamepadMapper)(uint16_t key,
+                              uint16_t code,
+                              GamepadEventType* mapped_type,
+                              uint16_t* mapped_code);
+
+// This function gets the best mapper for the gamepad vendor_id and product_id.
+GamepadMapper GetGamepadMapper(uint16_t vendor_id, uint16_t product_id);
+
+}  // namespace ui
+
+#endif  // UI_EVENTS_OZONE_GAMEPAD_GAMEPAD_MAPPING_H_