The source code

    Ext.state.SessionProvider = Ext.extend(Ext.state.CookieProvider, {
        readCookies : function(){
            if(this.state){
                for(var k in this.state){
                    if(typeof this.state[k] == 'string'){
                        this.state[k] = this.decodeValue(this.state[k]);
                    }
                }
            }
            return Ext.apply(this.state || {}, Ext.state.SessionProvider.superclass.readCookies.call(this));
        }
    });