MD Settings: Reset scroll when sliding subpages

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 78 matching lines @@
     var promise;
     var expandedSection = /** @type {?SettingsSectionElement} */(
         this.$$('settings-section.expanded'));
     if (expandedSection) {
       // If the section shouldn't be expanded, collapse it.
       if (!currentRoute.isSubpage() || expandedSection != currentSection) {
         promise = this.collapseSection_(expandedSection);
         // Scroll to the collapsed section.
         if (currentSection && !settings.lastRouteChangeWasPopstate())
           currentSection.scrollIntoView();
+      } else {
+        // Scroll to top while sliding to another subpage.
+        this.scroller.scrollTop = 0;
       }
     } else if (currentSection) {
       // Expand the section into a subpage or scroll to it on the main page.
       if (currentRoute.isSubpage())
         promise = this.expandSection_(currentSection);
       else if (!settings.lastRouteChangeWasPopstate())
         currentSection.scrollIntoView();
     }
 
     // When this animation ends, another may be necessary. Call this function
@@ skipping 189 matching lines @@
       this.scroller.style.width = 'calc(100% - ' + scrollbarWidth + 'px)';
     }
   }
 };
 
 /** @polymerBehavior */
 var MainPageBehavior = [
   settings.RouteObserverBehavior,
   MainPageBehaviorImpl,
 ];