[System-Keyboard-Lock] Add KeyboardLockHost and KeyEventInterceptor

components/keyboard_lock/keyboard_lock_types.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 COMPONENTS_KEYBOARD_LOCK_KEYBOARD_LOCK_TYPES_H_
+#define COMPONENTS_KEYBOARD_LOCK_KEYBOARD_LOCK_TYPES_H_
+
+#include <type_traits>
+#include <utility>
+
+#include "ui/events/keycodes/dom/keycode_converter.h"
+
+namespace keyboard_lock {
+
+// The type to represent a layout independent native keycode.
+// https://cs.chromium.org/chromium/src/ui/events/keycodes/dom/keycode_converter.h?l=36&gs=cpp%253Aui%253A%253A%253Calias-of-KeycodeMapEntry%253E%253A%253Anative_keycode%2540chromium%252F..%252F..%252Fui%252Fevents%252Fkeycodes%252Fdom%252Fkeycode_converter.h%257Cdef&gsn=native_keycode&ct=xref_usages
+// Though it equals to integer, most of the components in the keyboard_lock
+// expects it to be in range [0, 256). Keyboard events out of this range will
+// usually be ignored.
+typedef decltype(std::declval<ui::KeycodeMapEntry>().native_keycode)
+        NativeKeycode;
+
+static_assert(std::is_same<NativeKeycode, int>::value,
+              "Expect native_keycode to be int");
+
+}  // namespace keyboard_lock
+
+#endif  // COMPONENTS_KEYBOARD_LOCK_KEYBOARD_LOCK_TYPES_H_