您可以使用内容脚本在实际注入CSS之前检查是否已经注入了CSS，例如:

You can use a content script to check if the CSS was already injected before actually injecting it, like:

function myButtonClicked(){
    chrome.tabs.executeScript({code:`
        (function(){
            if (window.insertCSS === true) return false; //if already inserted return false;
            window.insertCSS = true;            //if not, set the page's variable and return it
            return true;
        })();
    `}, function (result) {
        if (result[0]) {  //if CSS was not inserted, insert it.
           chrome.tabs.insertCSS({file:'myCSS.css'});
        }
    });
}