Fix outdated documentation on blocking start and handling of synchronous requests

chrome/common/extensions/docs/samples.json

 {
   "api": {
     "chrome.alarms.clear": "alarms.html#method-clear",
     "chrome.alarms.clearAll": "alarms.html#method-clearAll",
     "chrome.alarms.create": "alarms.html#method-create",
     "chrome.alarms.get": "alarms.html#method-get",
     "chrome.alarms.getAll": "alarms.html#method-getAll",
     "chrome.alarms.onAlarm": "alarms.html#event-onAlarm",
     "chrome.app.window.create": "app.window.html#method-create",
     "chrome.app.window.focus": "app.window.html#method-focus",
@@ skipping 1395 matching lines @@
         "chrome.browserAction.setBadgeText",
         "chrome.browserAction.setIcon",
         "chrome.i18n.getMessage",
         "chrome.runtime.getBackgroundPage",
         "chrome.runtime.onInstalled",
         "chrome.tabs.create",
         "chrome.tabs.get",
         "chrome.tabs.update",
         "chrome.webNavigation.onDOMContentLoaded"
       ],
-      "crx_path": "examples/extensions/gmail.crx",
+      "crx_path": null,
       "description": "Displays the number of unread messages in your Google Mail inbox. You can also click the button to open your inbox.",
       "features": [
         "alarms",
         "background_page",
         "browser_action",
         "options_page",
         "tabs",
         "webNavigation"
       ],
       "icon": "icon_128.png",
@@ skipping 1388 matching lines @@
         "manifest.json",
         "popup.html",
         "popup.js",
         "sample.css"
       ],
       "source_hash": "8e51dc3a9577065d22ce92f3c838edc5ceaf4e65",
       "zip_path": "examples/api/extension/isAllowedAccess.zip"
     }
   ]
 }