Increase scaled-down label width to match 100% input width

Input label is shrunk using CSS `scale`. The 100% default width is
becoming smaller than full input width. Increasing accordingly the
shrunk input label `width` let it occupy as much space as possible,
avoiding in some case the wrapping of text, which is very inelegant in
this component.

packages/material-ui/src/Input/InputLabel.js

@@ -24,6 +24,7 @@ export const styles = theme => ({
   shrink: {
     transform: 'translate(0, 1.5px) scale(0.75)',
     transformOrigin: 'top left',
+    width: `${100 * 4 / 3}%`,
   },
   animated: {
     transition: theme.transitions.create('transform', {