Create unprefixed versions of pointerlockchange & pointerlockerror events.

LayoutTests/http/tests/resources/pointer-lock/pointer-lock-test-harness-prefixed.js

 // Automatically add doNextStepButton to document for manual tests.
 if (!window.testRunner) {
     setTimeout(function () {
         if (window.doNextStepButtonDisabled)
             return;
         doNextStepButton = document.body.insertBefore(document.createElement("button"), document.body.firstChild);
         doNextStepButton.onclick = doNextStep;
         doNextStepButton.innerText = "doNextStep button for manual testing. Use keyboard to select button and press (TAB, then SPACE).";
     }, 0);
 }
@@ skipping 68 matching lines @@
     eventExpected("onwebkitpointerlockerror", message, 1, targetDocument);
 };
 
 function expectNoEvents(message, targetDocument) {
     debug("     " + message);
     targetDocument = targetDocument !== undefined ? targetDocument : document;
     eventExpected("onwebkitpointerlockchange", message, 0, targetDocument);
     eventExpected("onwebkitpointerlockerror", message, 0, targetDocument);
 };