java/com/google/gwtexpui/user/client/tooltip.css

/* Copyright (C) 2015 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

.tooltip {
  position: relative;
}

.tooltip:hover:before {
  position: absolute;
  z-index: 51;
  border: solid;
  border-color: #333 transparent;
  border-width: 0 4px 4px 4px;
  pointer-events: none;
  content: "";

  top: auto;
  right: 50%;
  bottom: -5px;
  margin-right: -5px;
}

.tooltip:hover:after {
  position: absolute;
  z-index: 50;
  font: normal normal 11px/1.5 Helvetica, arial, sans-serif;
  text-align: center;
  white-space: pre;
  pointer-events: none;
  background: rgba(0,0,0,.7);
  color: #fff;
  border-radius: 3px;
  padding: 5px;
  content: attr(aria-label);

  top: 100%;
  right: 50%;
  margin-top: 5px;
  -webkit-transform: translateX(50%);
  -ms-transform: translateX(50%);
  transform: translateX(50%)
}