<!DOCTYPE html>
<!--
 | An unbreakable text box, which is the first box on a line, with an
 | "overflow-wrap" property value of "break-word", should not be
 | treated as having been split when it overflows the line.
 -->
<html>
<head>
  <style>
    body {
      margin: 0px;
      font-family: Roboto;
      font-size: 20px;
    }
    .containing-block {
      background-color: #03a9f4;
      width: 1px;
      overflow-wrap: break-word;
    }
  </style>
</head>
<body>
  <div class="containing-block">a</div>
</body>
</html>