MD Settings: Fix Back navigation from section route to BASIC route.

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

Index: chrome/browser/resources/settings/settings_page/main_page_behavior.js
diff --git a/chrome/browser/resources/settings/settings_page/main_page_behavior.js b/chrome/browser/resources/settings/settings_page/main_page_behavior.js
index 02fbbcc869fbf63d3493b6ec7a63d8b0936c3b25..e22580b8ea6b27e59a75bcfd4515ceefdfbe4a0b 100644
--- a/chrome/browser/resources/settings/settings_page/main_page_behavior.js
+++ b/chrome/browser/resources/settings/settings_page/main_page_behavior.js
@@ -30,6 +30,12 @@ var MainPageBehaviorImpl = {
     var oldRouteWasSection =
         !!oldRoute && !!oldRoute.parent && !!oldRoute.section &&
         oldRoute.parent.section != oldRoute.section;
+
+    if (oldRouteWasSection && newRoute == settings.Route.BASIC) {
+      this.scroller.scrollTop = 0;
+      return;
+    }
+
     var scrollToSection =
         !settings.lastRouteChangeWasPopstate() || oldRouteWasSection;