UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:49.0) Gecko/20100101 Firefox/49.0

Steps to reproduce the problem:
In the content script of an extension, execute the following code:
const textEvent = document.createEvent('TextEvent')
textEvent.initTextEvent('textInput',
            true,
            true,
            null,
            'myString');
document.activeElement.dispatchEvent(textEvent)

What is the expected behavior?
I expected that a Chrome extension could fire trusted events, and that the textInput TextEvent would trigger the default behaviour.

What went wrong?
Since Chrome 53, synthetic events do not trigger the default behaviour. I understand it is important for a regular website, but coming from the content script of an extension this is really blocking for me.

In Chrome 53 I had a workaround with document.execCommand('insertText', false, 'myString') that worked but shouldn't have. Not so suprisingly it doesn't work in Chrome 54.

Did this work before? Yes 52

Does this work in other browsers? N/A

Chrome version: <Copy from: 'about:version'>  Channel: n/a
OS Version: OS X 10.11
Flash Version: Shockwave Flash 23.0 r0