Use the unprefixed Pointer Lock API

chrome/test/data/extensions/platform_apps/web_view/pointerlock/inject_pointer_lock.js

 // Copyright 2013 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.
 
 var embedder = null;
 window.addEventListener('message', function(e) {
   var data = JSON.parse(e.data);
   if (data[0] == 'connect') {
     embedder = e.source;
     var msg = ['connected'];
     embedder.postMessage(JSON.stringify(msg), '*');
     return;
   }
 
   if (data == 'start-pointerlock') {
-    document.body.webkitRequestPointerLock();
+    document.body.requestPointerLock();
     return;
   }
 });
 
-document.addEventListener('webkitpointerlockchange', function(e) {
-  if (!!document.webkitPointerLockElement) {
+document.addEventListener('pointerlockchange', function(e) {
+  if (!!document.pointerLockElement) {
     var msg = ['acquired-pointerlock'];
     embedder.postMessage(JSON.stringify(msg), '*');
     return;
   }
   var msg = ['lost-pointerlock'];
   embedder.postMessage(JSON.stringify(msg), '*');
 });