DevTools: Run workspace mapping tip infobar animation only once

Source/devtools/front_end/sourcesView.css

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 98 matching lines @@
     background-color: rgb(255, 255, 255);
 }
 
 .source-frame-infobar-warning,
 .source-frame-infobar-error {
     background-color: rgb(255, 255, 194);
 }
 
 .source-frame-infobar {
     margin-top: 0;
+}
+
+.source-frame-infobar-animation {
     -webkit-animation: source-frame-infobar-reveal 0.1s;
 }
-
 @-webkit-keyframes source-frame-infobar-reveal {
     from { margin-top: -24px; }
     to { margin-top: 0; }
 }
 
 .source-frame-infobar-icon {
     background-image: url(Images/statusbarButtonGlyphs.png);
     background-size: 320px 144px;
     width: 11px;
     height: 10px;
@@ skipping 46 matching lines @@
 .source-frame-infobar-link {
     text-decoration: underline;
     color: rgb(50, 50, 200);
     cursor: pointer;
 }
 
 .source-frame-infobar-details-url {
     flex: 0 1000 auto;
     color: rgb(50, 50, 200);
 }