MD Settings: Skip unseen collapse animation

chrome/browser/resources/settings/settings_page/main_page_behavior.js

 // Copyright 2016 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.
 
 /**
  * Calls |readyTest| repeatedly until it returns true, then calls
  * |readyCallback|.
  * @param {function():boolean} readyTest
  * @param {!Function} readyCallback
  */
@@ skipping 192 matching lines @@
 
   /**
    * Animates the card in |section|, collapsing it back into its section.
    * @param {!SettingsSectionElement} section
    * @return {!Promise} Resolved when the transition is finished or canceled.
    */
   collapseSection_: function(section) {
     assert(this.scroller);
     assert(section.classList.contains('expanded'));
 
-    var canAnimateCollapse = section.canAnimateCollapse();
-    if (canAnimateCollapse) {
+    // Don't animate the collapse if we are transitioning between Basic/Advanced
+    // and About, since the section won't be visible.
+    var needAnimate =
+        settings.Route.ABOUT.contains(settings.getCurrentRoute()) ==
+        (section.domHost.tagName == 'SETTINGS-ABOUT-PAGE');
+
+    // Animate the collapse if the section knows the original height, except
+    // when switching between Basic/Advanced and About.
+    var shouldAnimateCollapse = needAnimate && section.canAnimateCollapse();
+    if (shouldAnimateCollapse) {
       this.toggleScrolling_(false);
       // Do the initial collapse setup, which takes the section out of the flow,
       // before showing everything.
       section.setUpAnimateCollapse(this.scroller);
     } else {
       section.classList.remove('expanded');
     }
 
     // Show everything.
     this.toggleOtherSectionsHidden_(section.section, false);
     this.classList.remove('showing-subpage');
 
-    if (!canAnimateCollapse) {
+    if (!shouldAnimateCollapse) {
       // Finish by restoring the section into the page.
       section.setFrozen(false);
       return Promise.resolve();
     }
 
     // Play the actual collapse animation.
     return new Promise(function(resolve, reject) {
       // Wait for the other sections to show up so we can scroll properly.
       setTimeout(function() {
         var newSection = settings.getCurrentRoute().section &&
@@ skipping 63 matching lines @@
       this.scroller.style.width = 'calc(100% - ' + scrollbarWidth + 'px)';
     }
   }
 };
 
 /** @polymerBehavior */
 var MainPageBehavior = [
   settings.RouteObserverBehavior,
   MainPageBehaviorImpl,
 ];