I know this is a little bit late, but I have to say there is a way to use <div>
with contenteditable
attribute to simulate desired behaviour.
.textareaElement {
width: 300px;
min-height: 17px;
border: 1px solid #ccc;
max-height: 150px;
overflow-x: hidden;
overflow-y: auto;
}
<div class="textareaElement" contenteditable></div>
Just set your min and max height, with proper overflow values, and you have fully functional pure CSS expanding textbox, that is also well supported.