palemoon-dev/platform/devtools/client/themes/layout.css

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#layoutview-container {
  height: 100%;
  width: 100%;
}

.layoutview-no-grids {
  font-style: italic;
  text-align: center;
  padding: 0.5em;
}