Touch events losing the `touches` property when fired in Chrome extension context

Question

I'm trying to simulate touch events from a Chrome extension. I'm using developer tools' in device mode in order to simulate a touch enabled browser.

When I run the code that simulates the touch event in the context of the document (selecting <top frame> in the developer tools drop down box) it works fine. However when I run the same code in the context of any extension (e.g. AdBlock) the touch event reaches the event handler without the touches and changedTouches properties (they are undefined).

Is this a defect in Chrome or am I missing something?

When I touch the red area I get the following output:

Got real touch event 1

(The 1 is the number of fingers touching).

When I simulate a touch I get the following output:

Got simulated touch event 1

If I copy the JavaScript into the dev-tools under the context of an extension

I get the following output:

Got real touch event null

(The real is because I don't have access to the captured simulated variable, this isn't relevant for this question).

Edit: I've submitted a bug report to the chromium project in case this is really a bug.

Code follows:

       var count = 0;

       function log(msg) {
         var out = document.getElementById('output');
         out.innerHTML = ++count + ': ' + msg + '<br/>' + out.innerHTML;
       }

       var simulated = false;

       function message() {
         return 'Got ' + (simulated ? 'simulated' : 'real') + ' touch event ';
       }

       function fire() {
         simulated = true;
         var event = document.createEvent('Event');
         event.initEvent('touchstart', true, true);
         var element = document.getElementById('x');
         event.touches = createTouchList(createTouch(element, {
           x: 5,
           y: 5
         }, 42));
         element.dispatchEvent(event);
       }
       window.fire = fire;

       function createTouch(element, point, id) {
         if (document.createTouch)
           return document.createTouch(window, element, id, point.x, point.y, point.x, point.y);

         return {
           view: window,
           target: element,
           identifier: id || 0,
           pageX: point.x,
           pageY: point.y,
           clientX: point.x,
           clientY: point.y
         };
       }

       function createTouchList(touches) {
         if (document.createTouchList)
           return document.createTouchList(touches);

         if (Array.isArray(touches))
           return touches;

         return [touches];
       }

       log('listening');
       document.getElementById('x').addEventListener('touchstart', function(e) {
         log(message() + (e.touches ? e.touches.length : 'null'));
         simulated = false;
       }, true);

 <h1 id="x" style="height: 50px; background-color: red; text-align:center">Touch here</h1>
<h1 onclick="fire()" style="height: 30px; background-color: cyan; text-align:center">Simulate touch event</h1>
<h3 id="output"></h3>