UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3443.0 Safari/537.36

Steps to reproduce the problem:
1. Open the example at https://codepen.io/anon/pen/WyeOxq?editors=1011 or try the code below:

    <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 320 240">
        <path id="p" d="M0,0C28.5,-23.5,61.5,-14.5,75,-5" stroke="#000000" fill="none" 
              transform="translate(36.5,62.5)"/>
    </svg>

    var p = document.getElementById("p").getPointAtLength(-10);
    console.log("getPointAtLength(-10): "+p.x+","+p.y);

    p = document.getElementById("p").getPointAtLength(0);
    console.log("getPointAtLength(0): "+p.x+","+p.y);

    p = document.getElementById("p").getPointAtLength(10);
    console.log("getPointAtLength(10): "+p.x+","+p.y);

2. Observe the console output
3. getPointAtLength(-10) should print "0,0" but it prints "-10,0"

What is the expected behavior?
getPointAtLength() should clamp its parameter to [0, length], but it doesn't: https://svgwg.org/svg2-draft/types.html#__svg__SVGGeometryElement__getPointAtLength

What went wrong?
getPointAtLength() allows negative values.

Did this work before? N/A 

Does this work in other browsers? No
 Safari 11 has a similar bug.
This works on Firefox 60.

Chrome version: 69.0.3443.0  Channel: canary
OS Version: OS X 10.12.6
Flash Version: