[MD settings] hide extra horizontal scrollbar

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

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="../a11y_page/a11y_page.html">
 <link rel="import" href="../appearance_page/appearance_page.html">
 <link rel="import" href="../controls/settings_idle_render.html">
 <link rel="import" href="../downloads_page/downloads_page.html">
 <link rel="import" href="../languages_page/languages_page.html">
 <link rel="import" href="../on_startup_page/on_startup_page.html">
 <link rel="import" href="../passwords_and_forms_page/passwords_and_forms_page.html">
 <link rel="import" href="../people_page/people_page.html">
 <link rel="import" href="../printing_page/printing_page.html">
@@ skipping 18 matching lines @@
 <if expr="not chromeos">
 <link rel="import" href="../default_browser_page/default_browser_page.html">
 <link rel="import" href="../system_page/system_page.html">
 </if>
 
 <!-- TODO(michaelpg): Rename to something better than "basic" now that this page
      includes both the basic and advanced settings. -->
 <dom-module id="settings-basic-page">
   <template>
     <style include="settings-page-styles">
+      :host {
+        /* Prevent an unwanted horizontal scrollbar when transitioning back from
+         * a sub-page. */
+        overflow: hidden;

[dpapad, 2017/03/16 20:51:19]

Does this create a problem when the page is too narrow? Ideally the user should
still be able to scroll left and right.

Perhaps it would be better to first understand why the scrollbar flashes on the
screen during the animation and possibly fix the root cause, instead of just
working around it?

[dschuyler, 2017/03/16 21:01:43]

The content is still fully accessible.
Can you be more specific about what you feel is incorrect?

[dpapad, 2017/03/16 21:13:52]

This suggestion was dependent on the question above. Since it works as expected,
it is not applicable. I should have made my comment more clear.

+      }
+
       #advancedToggle {
         --paper-button: {
           text-transform: none;
         }
         @apply(--settings-actionable);
         align-items: center;
         display: flex;
         margin-bottom: 3px;
         margin-top: 12px;  /* Part of a 48px spacer (33px + 12px + 3px). */
         min-height: 32px;
@@ skipping 219 matching lines @@
                 section="reset">
               <settings-reset-page></settings-reset-page>
             </settings-section>
           </template>
         </div>
       </template>
     </template>
   </template>
   <script src="basic_page.js"></script>
 </dom-module>