Disable wallpaper button in Guest mode settings

chrome/browser/resources/options/browser_options.js

Index: chrome/browser/resources/options/browser_options.js
diff --git a/chrome/browser/resources/options/browser_options.js b/chrome/browser/resources/options/browser_options.js
index 1bc711f8e33eaccc7c1fde4d77f5493a1b866c1f..fa610e35421ca8d79fbb4c7867416732bb485f1b 100644
--- a/chrome/browser/resources/options/browser_options.js
+++ b/chrome/browser/resources/options/browser_options.js
@@ -1492,8 +1492,10 @@ cr.define('options', function() {
      * @param {boolean} managed
      */
     setWallpaperManaged_: function(managed) {
-      var button = $('set-wallpaper');
-      button.disabled = !!managed;
+      if (managed)
+        $('set-wallpaper').disabled = true;
+      else
+        this.enableElementIfPossible_($('set-wallpaper'));
 
       // Create a synthetic pref change event decorated as
       // CoreOptionsHandler::CreateValueForPref() does.
@@ -1939,6 +1941,18 @@ cr.define('options', function() {
     handleSetTime_: function() {
       chrome.send('showSetTime');
     },
+
+    /**
+     * Enables the given element if possible; on Chrome OS, it won't enable
+     * an element that must stay disabled for the session type.
+     * @param {!Element} element Element to enable.
+     */
+    enableElementIfPossible_: function(element) {
+      if (cr.isChromeOS)
+        UIAccountTweaks.enableElementIfPossible(element);
+      else
+        element.disabled = false;
+    },
   };
 
   //Forward public APIs to private implementations.