UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36

Steps to reproduce the problem:
1. Create a document containing nothing but the following markup:
```
<form action="/">
  <input type="search" name="q">
</form>
```
2. Run the following snippet of JavaScript:
```
document.body.addEventListener('keypress', function(e) {
  const inputElem = document.querySelector('input');
	const previousValue = inputElem.value;
  inputElem.value = previousValue + e.key;
  inputElem.focus();
});
```
3. Without focussing the input, press the "a" button on your keyboard.

What is the expected behavior?
The input field should now be in a focused state and contain the letter "a".

What went wrong?
The input field contains the letter "a" twice.

Did this work before? N/A 

Chrome version: 58.0.3029.110  Channel: stable
OS Version: 
Flash Version: Shockwave Flash 25.0 r0

Online fiddle to reproduce the issue: https://jsfiddle.net/s1Lztfne/

Works as expected in other major browsers.