Authenticating a Cognito User in Browser JS using tokens from cognito itself as an Identity provider

Hi,

We have a multiplatform app consisting in an Android app and a website that share a User Pool for the login procedure. In the browser, for the login, we use without any problem the flow described in case 4 @ https://www.npmjs.com/package/amazon-cognito-identity-js :

var authenticationData = {
	Username: 'username',
	Password: 'password',
};
var authenticationDetails = new AmazonCognitoIdentity.AuthenticationDetails(
	authenticationData
);
var poolData = {
	UserPoolId: '...', // Your user pool id here
	ClientId: '...', // Your client id here
};
var userPool = new AmazonCognitoIdentity.CognitoUserPool(poolData);
var userData = {
	Username: 'username',
	Pool: userPool,
};
var cognitoUser = new AmazonCognitoIdentity.CognitoUser(userData);
cognitoUser.authenticateUser(authenticationDetails, {
	onSuccess: function(result) {
  (...)

We also have an android application where users can also login using the Amplify framework, the login works as described in https://docs.amplify.aws/lib/auth/signin/q/platform/android/#sign-in-a-user

Amplify.Auth.signIn("username", "password",
    { result ->
        if (result.isSignInComplete) {
            Log.i("AuthQuickstart", "Sign in succeeded")
        } else {
            Log.i("AuthQuickstart", "Sign in not complete")
        }
    },
    { Log.e("AuthQuickstart", "Failed to sign in", it) }
)

But, now, we need to authenthicate the users in another browser scenario (a webview inside the android Application) without asking for a password or username (as they are using the app, they already logged), I guess using the tokens generated in the Android login. I don't see any way to do such an authenthication using methods described in: https://www.npmjs.com/package/amazon-cognito-identity-js

I'm tempted to use in the browser webView, as described in https://docs.aws.amazon.com/sdk-for-javascript/v2/developer-guide/loading-browser-credentials-cognito.html,

AWS.config.credentials = new AWS.CognitoIdentityCredentials({
  IdentityPoolId: '<the pool that is shared by android and browser app>',
  Logins: { 
					'cognito-idp.<region>.amazonaws.com/<the_POOL_ID>': <the_jwt_token_derived_from_the_android_login?>,
  }
});

But this is not working at all. The AWS.config.Credentials show an expired token and no login has been made, I cannot retrieve a Cognito Session. Does anyone know how to handle this situation?

Thanks in advance for you time