ntp4: disable animations for pages that are off screen

chrome/browser/resources/ntp4/tile_page.css

 /* Copyright (c) 2011 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.
  */
 
 .tile-page {
   height: 100%;
   position: relative;
   width: 100%;
 }
@@ skipping 136 matching lines @@
     -webkit-animation-timing-function: linear;
     -webkit-transform: scale(0.3, 0.02);
   }
 }
 
 .tile > .removing-tile-contents {
   pointer-events: none;
   -webkit-animation: blipout 0.3s;
 }
 
+.tile-page:not(.selected-card) * {
+  -webkit-transition: none !important;
+}
+
 /** Scrollbars ****************************************************************/
 
 .tile-page-content::-webkit-scrollbar {
   width: 13px;
 }
 
 .tile-page-content::-webkit-scrollbar-button {
   display: none;
 }