MD Settings: Prevent erroneous scroll when navigating subpage->subpage.

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.
 
 /**
  * Responds to route changes by expanding, collapsing, or scrolling to sections
  * on the page. Expanded sections take up the full height of the container. At
  * most one section should be expanded at any given time.
  * @polymerBehavior MainPageBehavior
  */
@@ skipping 272 matching lines @@
     }
 
     // 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 &&
             this.getSection(settings.getCurrentRoute().section);
 
         // Scroll to the new section or the original position.
-        if (newSection && !settings.lastRouteChangeWasPopstate())
+        if (newSection && !settings.lastRouteChangeWasPopstate() &&
+            !settings.getCurrentRoute().isSubpage()) {
           newSection.scrollIntoView();
-        else
+        } else {
           this.scroller.scrollTop = this.origScrollTop_;
+        }
 
         this.currentAnimation_ = section.animateCollapse(
             /** @type {!HTMLElement} */(this.scroller));
 
         this.currentAnimation_.finished.catch(function() {
           // The collapse was canceled, so the page is showing a subpage still.
           this.fire('subpage-expand');
         }.bind(this)).then(function() {
           // Clean up after the animation succeeds or cancels.
           section.setFrozen(false);
@@ skipping 31 matching lines @@
     return /** @type {?SettingsSectionElement} */(
         this.$$('settings-section[section="' + section + '"]'));
   },
 };
 
 /** @polymerBehavior */
 var MainPageBehavior = [
   settings.RouteObserverBehavior,
   MainPageBehaviorImpl,
 ];