[System-Keyboard-Lock] Add KeyboardLockHost and KeyEventInterceptor

components/keyboard_lock/key_event_interceptor_installer.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/key_event_interceptor_installer.h"
+
+#include <memory>
+
+#include "base/logging.h"
+#include "components/keyboard_lock/keyboard_lock_host.h"
+
+namespace keyboard_lock {
+
+KeyEventInterceptorInstaller::KeyEventInterceptorInstaller(
+    KeyboardLockHost* host)
+    : host_(host) {
+  DCHECK(host_);
+}
+
+void KeyEventInterceptorInstaller::Install() {
+  host_->SetKeyEventInterceptor(std::unique_ptr<KeyEventInterceptor>(this));
+}
+
+KeyEventInterceptorInstaller::~KeyEventInterceptorInstaller() = default;
+
+}  // namespace keyboard_lock