所以我认为简单的解决方案就是创建一个内容脚本并在那里等到页面加载：

So I think that the simple solution is just to create a content script and there to wait until the page is load :

manifest.json

manifest.json

{

 "manifest_version": 2,
 "name": "Getting started example",
"description": "This extension shows a Google Image search result for the   current page",
"version": "1.0",
"content_scripts": [
 {
    //Set your address you want the extension will work in mataches!!! 
 "matches": ["http://mail.google.com/*", "https://mail.google.com/*"],
  "js": ["content.js"],
  "run_at": "document_end"
 }
],  
"permissions": [
              "activeTab",
"https://ajax.googleapis.com/"
             ],
 "browser_action": {
 "default_icon": "icon.png",
 "default_popup": "popup.html"
 }

}

content.js

content.js

window.onload=function(){
     console.log("page load!");
}

您还可以使用background.js和内容页面之间的消息传递检查选项卡是否已加载，但对于您的情况，我认为这已经足够了。

You could also use with message passing between background.js and your content page and to check that tab is loaded but for your case I think it's enough.