static/ext/src/data/flash/BinaryXhr.js
function (method, url, async, user, password) {
        var me = this;
        me.method = method;
        me.url = url;
        me.async = async !== false;
        me.user = user;
        me.password = password;
        
        //<debug>
        if (!me.async) {
            Ext.Error.raise("Binary posts are only supported in async mode: " + url);
        }
        if (me.method != "POST") {
            Ext.log.warn("Binary data can only be sent as a POST request: " + url);
        }
        //</debug>
    }
function (method, url, async, user, password) {
        var me = this;
        me.method = method;
        me.url = url;
        me.async = async !== false;
        me.user = user;
        me.password = password;
        
        //<debug>
        if (!me.async) {
            Ext.Error.raise("Binary posts are only supported in async mode: " + url);
        }
        if (me.method != "POST") {
            Ext.log.warn("Binary data can only be sent as a POST request: " + url);
        }
        //</debug>
    }
As in XMLHttpRequest.