Hovering a Chrome field-suggestion shrinks input - html

Question

I'm using the latest version of Chrome (74.0.3729.169) and noticed something slightly frustrating/interesting.
In the example below, begin typing an email address that you've used before. Once Chrome's suggestions appear, hover over one of them. Notice how dramatically the input shrinks.
input { padding: 5px; border: 1px solid #ccc; }
<input id="email" name="email" type="text" placeholder="Email">
I apologize if this doesn't recreate the behavior, however I've now been able to recreate it with this snippet across multiple computers, so I'm fairly confident this should work.
Additionally (to dip my toes into Meta a bit here) there's a fairly dramatic example of this on StackOverflow's very own login screen, in which the entire form shrinks as a result.
Compare the width of the two images below. Or, in the second image, compare the width of the "suggestion" with the input to which it corresponds.
From inspecting the input itself, I don't see any new styles that would explain this behavior. It doesn't seem related to padding either, as an input without padding still demonstrates this behavior.
My question is two-fold: Why does hovering a suggestion cause the input to shrink, and, is there a method/workaround to prevent this, other than fixed width or disabling suggestions entirely?
(I think that both of these workarounds are conditional. There are instances where you may not want to specify an input width for styling purposes, and disabling suggestions seems excessive and harmful to UX)
Or perhaps a Chromium bug ticket somewhere (I've searched with no luck - googling anything related to Chrome's autofill/autocomplete is a mess of unrelated articles about security)?

Answer 1

What you are facing is related to :-webkit-autofill pseudo class that is applying some default styling to the input with an autocomplete.
The :-webkit-autofill CSS pseudo-class matches when an element has its value autofilled by the browser.
Unnfortunately, I am not able to find where exactly those styles are defined but here is an example to confirm this. If you try to use the same value of width you will avoid the shrink effect:
:-webkit-autofill {
width: 173px;
}
<input id="email" name="email" type="text" placeholder="Email">
In the above link you can also read:
Note: The user agent style sheets of many browsers use !important in their :-webkit-autofill style declarations, making them non-overrideable by webpages without resorting to JavaScript hacks.
So even with !important you won't be able to override some styles:
:-webkit-autofill {
width: 173px;
background:red!important; /* will not work*/
border:2px solid blue;
margin-left:150px;
}
<input id="email" name="email" type="text" placeholder="Email">
For the width issue, I guess the only way is to define an explicit width as I have tried auto, initial, unset, etc and they aren't working.
If you cannot set a width and you want the default one, you can consider JS to do this:
document.querySelector('#email').style.width=document.querySelector('#email').offsetWidth+"px";
<input id="email" name="email" type="text" placeholder="Email">