Refactors away method implementations in ui::EventTargeter

ui/events/null_event_targeter.cc

 // Copyright 2015 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 "base/logging.h"
 #include "ui/events/null_event_targeter.h"
 
 namespace ui {
 
 NullEventTargeter::NullEventTargeter() {
 }
 
 NullEventTargeter::~NullEventTargeter() {
 }
 
 EventTarget* NullEventTargeter::FindTargetForEvent(EventTarget* root,
                                                    Event* event) {
   return nullptr;
 }
 
+EventTarget* NullEventTargeter::FindNextBestTarget(EventTarget* previous_target,
+                                                   Event* event) {
+  NOTREACHED();
+  return nullptr;
+}
+
 }  // namespace ui