Fix the event page sample extension to say "event page".

chrome/common/extensions/docs/examples/api/eventPage/basic/content.js

 // Copyright (c) 2012 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.
 
 document.body.innerHTML = "";
 
 function addButton(name, cb) {
   var a = document.createElement("button");
   a.innerText = name;
   a.onclick = cb;
@@ skipping 30 matching lines @@
 chrome.extension.onMessage.addListener(function(msg, _, sendResponse) {
   log("Got message from background page: " + msg);
 });
 
 var logDiv = document.createElement("div");
 logDiv.style.border = "1px dashed black";
 document.body.appendChild(document.createElement("br"));
 document.body.appendChild(logDiv);
 
 log("Ready.");