help: add important animation to Chrome logo.

chrome/browser/resources/help/help_content.css

 /* Copyright 2014 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #about-container {
   align-items: center;
   display: flex;
   margin-top: 10px;
 }
 
 #product-description {
   -webkit-margin-start: 10px;
 }
 
+@-webkit-keyframes spin {
+  to { transform: rotate(-10turn); }
+}
+
+#product-logo.spin {
+  -webkit-animation: spin 500ms cubic-bezier(1, 0, 0, 1) forwards;
+}
+
 #version-container {
   margin-top: 30px;
 }
 
 #update-buttons-container {
   margin-top: 5px;
 }
 
 #update-status-container {
   margin-top: 10px;
@@ skipping 106 matching lines @@
   background-size: 22px;
   vertical-align: top;
 }
 
 .channel-change-error-text {
   -webkit-margin-start: 4px;
   display: block;
   vertical-align: top;
   width: 240px;
 }