Cut the mustard with proxy browsers taken into consideration

mustard-test.js

var hasStorage = (function() {
    try {
        localStorage.setItem("test", "mod" );
        localStorage.removeItem("test");
        return true;
    } catch (exception) {
        // console.info(exception);
        if (exception && exception.name=="QuotaExceededError" && localStorage.length == 0) {
            //private
            return true;
        } else {
            return false;
        }
    }
}());

if( 'querySelector' in document && hasStorage && 'addEventListener' in window ){
//cuts the mustard  
}

I think it can be a little shorter, taking out one of those return true statements if the if statement is inverted. Also, I mentioned http://chrisberkhout.com/blog/localstorage-errors/ for the exception name, but I can't find a list of possible exceptions.

Also, if storage is full (possible, not likely) it would return false as well