wired-combo does not expand

Issue Description

I am unable to make the wired-combo element of any other width then it's default, the wired-input element expands nicely when given a width, but the wired-combo only expands it's container while the id="textPanel" element remains the same width

CodeSandbox

The simplest example, I have tried some other selector variants, but nothing works for me :(

link to sandbox

Proposed solution

It would be best if the elements just filled the container and then we would be able to control it's width very easily