Update more extension manifests to manifest_version 2

chrome/test/data/extensions/devtools/timeline_api/background.html

-<script>
-
-var receivedEvents = [];
-var devtoolsTabEvents = undefined;
-
-function pageEventListener() {
-  receivedEvents.push("onPageEvent");
-}
-
-function tabCloseListener() {
-  receivedEvents.push("onTabClose");
-}
-
-function setListenersOnTab(tabId) {
-  try {
-    devtoolsTabEvents = chrome.devtools.getTabEvents(tabId);
-    devtoolsTabEvents.onPageEvent.addListener(pageEventListener);
-    devtoolsTabEvents.onTabClose.addListener(tabCloseListener);
-    window.domAutomationController.send(true);
-  } catch(e) {
-    window.domAutomationController.send(false);
-  }
-}
-
-function testReceivePageEvent() {
-  if (receivedEvents.length == 1) {
-    var eventName = receivedEvents.pop();
-    window.domAutomationController.send(eventName === "onPageEvent");
-  } else {
-    receivedEvents = [];
-    window.domAutomationController.send(false);
-  }
-}
-
-function testReceiveTabCloseEvent() {
-  if (receivedEvents.length == 1) {
-    var eventName = receivedEvents.pop();
-    window.domAutomationController.send(eventName === "onTabClose");
-  } else {
-    receivedEvents = [];
-    window.domAutomationController.send(false);
-  }
-}
-
-function unregisterListeners() {
-  devtoolsTabEvents.onPageEvent.removeListener(pageEventListener);
-  devtoolsTabEvents.onTabClose.removeListener(tabCloseListener);
-  window.domAutomationController.send(true);
-}
-
-</script>
+<!--
+ * 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.
+-->
+<script src="background.js"></script>