かなりいいところまで来てる

server.console.md

server console

# 試験系
POST
ImmutableMultiDict([('img', <FileStorage: u'' ('application/octet-stream')>)])
<FileStorage: u'' ('application/octet-stream')>
124.35.46.4 - - [12/Sep/2013 00:28:31] "POST /upload HTTP/1.1" 500 -

# 正常系
POST
ImmutableMultiDict([('img', <FileStorage: u'sample03.png' ('image/png')>)])
<FileStorage: u'sample03.png' ('image/png')>
124.35.46.4 - - [12/Sep/2013 00:28:49] "POST /upload HTTP/1.1" 200 -

client code

        var xhr = new XMLHttpRequest();
        xhr.open('POST', 'http://myhost.com:9999/upload');

        var form = document.createElement('form');
        var input = document.createElement('input');
        input.type = 'file';
        input.name = 'img';
        //input.value = dataUrl;
        form.appendChild(input);
        var data = new FormData(form);

        xhr.send(data);

        xhr.addEventListener('load',function(ev){
            if(xhr.status !== 200) return alert(xhr.status);
            alert(xhr.response);
        });

http://hebikuzure.wordpress.com/2012/12/16/file-api-%E3%81%A7%E4%BD%9C%E6%88%90%E3%81%97%E3%81%9F-blob-%E3%82%92%E3%83%80%E3%82%A6%E3%83%B3%E3%83%AD%E3%83%BC%E3%83%89%E3%81%99%E3%82%8B/

ｱｶﾝこれ無理な奴や
http://oshiete.goo.ne.jp/qa/1794854.html

input[type=file]じゃなくて、バイナリで攻める
http://d.hatena.ne.jp/yoya/20130425/jsbin

chrome.tabs.captureVisibleTabがbinary返してくれればよかったのに