body, html {
  margin: 0;
  height: 100%;
}
div.row {
  width: calc(100% - 60px);
  height: calc(100% - 60px);
}
.stream {
  position: relative;
  vertical-align: text-top;
  display: inline-block;
  width: 100%;
  height: 100%;
  border-right: 1px solid #000;
  border-bottom: 1px solid #000;
  box-sizing: border-box;
}
  .stream span.close {
    position: absolute;
    top: 4px;
    right: 4px;
    line-height: 8px;
    background: #FFF;
    padding: 6px;
    z-index: 2;
    border: 1px solid #000;
    border-radius: 4px;
    display: none;
  }

  .stream:hover span.close {
    display: block;
  }

  .stream:hover span.close:hover {
    cursor: pointer;
  }
div#addColumn, div#addRow {
  position: absolute;
  border: 1px solid #000;
  box-sizing: border-box;
  text-align: center;
  line-height: 60px;
  font-size: 20pt;
}

div#addColumn:hover, div#addRow:hover {
  cursor: pointer;
  background-color: #CCC;
}
div#addColumn {
  right: 0;
  top: 0;
  bottom: 60px;
  width: 60px;
  -ms-writing-mode: tb-lr;
  -webkit-writing-mode: vertical-lr;
  -moz-writing-mode: vertical-lr;
  -ms-writing-mode: vertical-lr;
  writing-mode: vertical-lr;
}
div#addRow {
  bottom: 0;
  right: 0;
  left: 0;
  height: 60px;
}