aura: Add back XInputHierarchyChangedEventListener for aura and remove stubs.

chrome/browser/chromeos/xinput_hierarchy_changed_event_listener_aura.cc

Index: chrome/browser/chromeos/xinput_hierarchy_changed_event_listener_aura.cc
diff --git a/chrome/browser/chromeos/xinput_hierarchy_changed_event_listener_aura.cc b/chrome/browser/chromeos/xinput_hierarchy_changed_event_listener_aura.cc
new file mode 100644
index 0000000000000000000000000000000000000000..16413488c01115af9d77fb88abea1b2d7e0cf596
--- /dev/null
+++ b/chrome/browser/chromeos/xinput_hierarchy_changed_event_listener_aura.cc
@@ -0,0 +1,30 @@
+// Copyright (c) 2011 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 "chrome/browser/chromeos/xinput_hierarchy_changed_event_listener.h"
+
+namespace chromeos {
+
+void XInputHierarchyChangedEventListener::Init() {
+  MessageLoopForUI::current()->AddObserver(this);
+}
+
+void XInputHierarchyChangedEventListener::StopImpl() {
+  MessageLoopForUI::current()->RemoveObserver(this);
+}
+
+base::EventStatus XInputHierarchyChangedEventListener::WillProcessEvent(
+    const base::NativeEvent& event) {
+  // There may be multiple listeners for the XI_HierarchyChanged event. So
+  // always return EVENT_CONTINUE to make sure all the listeners receive the
+  // event.
+  ProcessedXEvent(event);
+  return base::EVENT_CONTINUE;
+}
+
+void XInputHierarchyChangedEventListener::DidProcessEvent(
+    const base::NativeEvent& event) {
+}
+
+}  // namespace chromeos