The result of subarray of another subarray is wrong. Test code:

            var arr = new Uint8Array([1,2,3,4,5,6,7,8,9,10]);
            var sub1 =arr.subarray(5,10);
            var sub1a=[];
            for(var i=0;i<sub1.length;i++)
                sub1a.push(sub1[i]);
            console.log('sub1='+sub1a);
            var sub2 =sub1.subarray(0,3);
            var sub2a=[];
            for(var i=0;i<sub2.length;i++)
                sub2a.push(sub2[i]);
            console.log('sub2='+sub2a);

In htmlunit, the output is:

sub1=6,7,8,9,10
sub2=1,2,3

The correct result or the result from real browser is:

sub1=6,7,8,9,10
sub2=6,7,8