Latest Chrome 52 Canary on Mac

Ran CM API command no https://flipboard.com/signin

function processResponse(cred) {
cred.idName='username';
cred.additionalData=new URLSearchParams();
cred.additionalData.append('_csrf', csrf_from_page_source);
fetch('/api/flipboard/login',{credentials:cred, method:'POST'}).then(a => window.location = '/');
}
navigator.credentials.get({password: true}).then(processResponse).catch(e => console.log(e));

Don't see the form data POST body in the network tab of the console

Request URL:https://flipboard.com/api/flipboard/login
Request Method:POST
Status Code:200 OK
Remote Address:52.21.53.188:443
Response Headers
view source
Accept-Ranges:bytes
Access-Control-Allow-Credentials:true
Access-Control-Allow-Methods:HEAD, GET, POST, PUT, DELETE, OPTIONS
Access-Control-Allow-Origin:https://flipboard.com
Access-Control-Expose-Headers:fl-job-id
Access-Control-Max-Age:86400
Age:0
Cache-Control:no-cache
Connection:keep-alive
Content-Encoding:gzip
Content-Length:562
Content-Type:application/json; charset=utf-8
Date:Tue, 10 May 2016 01:34:55 GMT
fl-job-id:127.0.0.1:40568
Set-Cookie:userid=1617823694; Domain=.flipboard.com; Path=/; Expires=Thu, 10 May 2018 01:34:55 GMT
Set-Cookie:fid2=flap-7ca6b3ee-0504-41a2-a019-6987566a9e11; max-age=1200; path=/
Set-Cookie:access_token=1617823694%7C6ce7c919637b834ee95ac8d1f329aa4a%7C12b5eacaccf4e6d86d547e499317c33f; Domain=.flipboard.com; Path=/; Expires=Thu, 10 May 2018 01:34:55 GMT; HttpOnly; Secure
Set-Cookie:flap=6215d9e5; max-age=1200; path=/
Set-Cookie:sid2=2b21c713-593b-4196-916f-fbd8801548e1; max-age=1800; path=/
Vary:Accept-Encoding
Via:1.1 varnish-v4
X-Content-Type-Options:nosniff
X-Powered-By:Express
X-Varnish:38644416
X-Varnish-Cache:MISS
Request Headers
view source
Accept:*/*
Accept-Encoding:gzip, deflate
Accept-Language:en-US,en;q=0.8
Connection:keep-alive
Content-Length:188
content-type:application/x-www-form-urlencoded;charset=UTF-8
Cookie:request_token=59446cb0ab871ddfc13ad8dde9364c7d%7C338e91602870c6a9d13f53d8557a001b%7C61b602fddd0b552b89aeac6f333a6c92; _gat=1; fid2=flap-7ca6b3ee-0504-41a2-a019-6987566a9e11; sid2=53e6ca4b-9428-47d8-af6d-d7eef6e8d913; flap=6215d9e5; _csrfKey=t%2FL3LHT6ZI30fi1iGXAaIVQW%2Bu8%3D%7C0%7CHFAVwV58i54nRDdquXsN1271BOFD172%2B8x4%2Ba8K%2BlXxT8YceyHYE1M%2BpTtGEKr6Qqh%2F2ITliaENXc%2FglcYH9Cg%3D%3D; _ga=GA1.2.1130014115.1457664095
Host:flipboard.com
Origin:https://flipboard.com
Referer:https://flipboard.com/signin
User-Agent:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2729.0 Safari/537.36