Previously, empty text boxes would fall back to the min-height: 16px
set on the <input> element. As soon as there is any content they
would usually gain height because the line height of that text is
more than 16px (depending on the font/font-size used).
Now they use height: 1lh for the inner div (which contains the
actual text), which matches the exact height of 1 line of content.
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