[MD settings] hide scrollbar during animation to subpage

chrome/browser/resources/settings/basic_page/basic_page.html

Index: chrome/browser/resources/settings/basic_page/basic_page.html
diff --git a/chrome/browser/resources/settings/basic_page/basic_page.html b/chrome/browser/resources/settings/basic_page/basic_page.html
index a16666643d5194c66b309539b5565744bd85f9a5..206c4b053f0ee2745705d5bab10062497592dc8b 100644
--- a/chrome/browser/resources/settings/basic_page/basic_page.html
+++ b/chrome/browser/resources/settings/basic_page/basic_page.html
@@ -27,6 +27,12 @@
 <dom-module id="settings-basic-page">
   <template>
     <style include="settings-page-styles">
+      :host([is-subpage-animating]) {
+        /* Prevent an unwanted horizontal scrollbar when transitioning back from
+         * a sub-page. */
+        overflow: hidden;
+      }
+
       #advancedToggle {
         --paper-button: {
           text-transform: none;