Keyboard Lock Host implementation

components/keyboard_lock/active_key_event_filter_tracker.cc

Index: components/keyboard_lock/active_key_event_filter_tracker.cc
diff --git a/components/keyboard_lock/active_key_event_filter_tracker.cc b/components/keyboard_lock/active_key_event_filter_tracker.cc
new file mode 100644
index 0000000000000000000000000000000000000000..30195fe725ed046a97676410ffc18cd8eaf4b7df
--- /dev/null
+++ b/components/keyboard_lock/active_key_event_filter_tracker.cc
@@ -0,0 +1,31 @@
+// 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/active_key_event_filter_tracker.h"
+
+#include "base/logging.h"
+
+namespace keyboard_lock {
+
+ActiveKeyEventFilterTracker::ActiveKeyEventFilterTracker() = default;
+ActiveKeyEventFilterTracker::~ActiveKeyEventFilterTracker() = default;
+
+void ActiveKeyEventFilterTracker::set(KeyEventFilter* filter) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  filter_ = filter;
+}
+
+void ActiveKeyEventFilterTracker::erase(const KeyEventFilter* filter) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (filter_ == filter) {
+    filter_ = nullptr;
+  }
+}
+
+KeyEventFilter* ActiveKeyEventFilterTracker::get() const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  return filter_;
+}
+
+}  // namespace keyboard_lock