Script injection on mail.google.com using chrome extension - google-chrome-extension

Question

I am working on a chrome extension in which I am replacing the chrome's web API function navigator.credentials.create with a custom handler. navigator.credentials.create is called when a user initiates a 2FA registration for a security key.
The custom handler is working on facebook.com but, it doesn't work on mail.google.com.
I have attached the minimal code for the extension I'm working on. This script is injected on every page and can be confirmed through console "injected script". In my sample app, I printed a console statement "In extension's create" in the custom handler of navigator.credentials.create. This should be printed whenever a user initiates the 2FA registration process. It is working for facebook but doesn't work on https://myaccount.google.com/. I have verified that the script is inserted in all iframes available on the website. I also confirmed that mail.google.com is not using service workers to call navigator.credentials.create API.
content_script.js
const webauthnInject = document.createElement('script');
webauthnInject.type = 'text/javascript';
webauthnInject.src = 'chrome-extension://' + chrome.runtime.id + '/inject_webauthn.js';
document.documentElement.appendChild(webauthnInject);
inject_webauthn.js
(() => {
console.log("injected script");
const real_create = navigator.credentials.create;
navigator.credentials.create = async function() {
console.log("In extension's create");
let res = await real_create.bind(navigator.credentials)(arguments[0]);
return res;
};
})();
manifest.json
{
"manifest_version": 2,
"name": "sample app",
"description": "A Sample app",
"version": "1.0.2",
"minimum_chrome_version": "36.0.1985.18",
"content_scripts": [
{
"all_frames": true,
"match_about_blank": true,
"matches": [
"https://*/*",
"http://*/*"
],
"exclude_matches": [
"https://*/*.xml"
],
"run_at": "document_start",
"js": [
"content_script.js"
]
}
],
"background": {
"persistent": false,
"scripts": [
"background.js"
]
},
"content_security_policy": "script-src 'self' 'unsafe-eval'; object-src 'self'",
"permissions": [
"tabs",
"storage",
"https://*/*",
"http://*/*"
],
"web_accessible_resources": [
"inject_webauthn.js"
]
}