[System-Keyboard-Lock] Add KeyboardLockHost and KeyEventInterceptor

components/keyboard_lock/keyboard_lock_host_unittest.cc

+// 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.
+
+#include "components/keyboard_lock/keyboard_lock_host.h"
+
+#include "base/message_loop/message_loop.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace keyboard_lock {
+
+// This is a placeholder test to ensure keyboard_lock component is correctly
+// referred and built.
+TEST(KeyboardLockHostTest, Construct) {
+  base::MessageLoop loop;
+  KeyboardLockHost host(loop.task_runner());
+}
+
+}  // namespace keyboard_lock