date and time inputs are not streched inside a flexbox

[CYBAI]

Servo	Firefox 76.0.1

<style>
.container {
  width: 300px;
  background-color: red;
}

.body {
  display: flex;
  padding: 12px 16px;
}

.date {
  flex-grow: 1;
  margin-right: 4px;
}

.date input, .time input {
  padding-left: 12px;
  padding-right: 20px;
}
</style>

<div class=container>
  <div class="body">
    <div class="date">
      <input type="date">                      
    </div>
    <div class="time">
      <input type="time">
    </div>
  </div>
</div>

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