Fix wallpaper button in Guest mode settings

R=stevenjb@chromium.org
BUG=401640

Review URL: https://codereview.chromium.org/599723002

Cr-Commit-Position: refs/heads/master@{#299046}

chrome/browser/resources/options/browser_options.js

@@ -1508,16 +1508,15 @@ 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.
       var event = new Event('wallpaper');
-      if (managed)
-        event.value = { controlledBy: 'policy' };
-      else
-        event.value = {};
+      event.value = managed ? { controlledBy: 'policy' } : {};
       $('wallpaper-indicator').handlePrefChange(event);
     },
 
@@ -1968,6 +1967,18 @@ 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.

ui/webui/resources/js/chromeos/ui_account_tweaks.js

@@ -56,6 +56,26 @@ cr.define('uiAccountTweaks', function() {
     return loadTimeData.getBoolean('loggedInAsSupervisedUser');
   };
 
+  /**
+   * Enables an element unless it should be disabled for the session type.
+   *
+   * @param {!Element} element Element that should be enabled.
+   */
+  UIAccountTweaks.enableElementIfPossible = function(element) {
+    var sessionType;
+    if (UIAccountTweaks.loggedInAsGuest())
+      sessionType = SESSION_TYPE_GUEST;
+    else if (UIAccountTweaks.loggedInAsPublicAccount())
+      sessionType = SESSION_TYPE_PUBLIC;
+
+    if (sessionType &&
+        element.getAttribute(sessionType + '-visibility') == 'disabled') {
+      return;
+    }
+
+    element.disabled = false;
+  }
+
   /**
    * Disables or hides some elements in specified type of session in ChromeOS.
    * All elements within given document with *sessionType*-visibility
@@ -68,10 +88,10 @@ cr.define('uiAccountTweaks', function() {
    */
   UIAccountTweaks.applySessionTypeVisibility_ = function(document,
                                                          sessionType) {
-    var elements = document.querySelectorAll('['+ sessionType +'-visibility]');
+    var elements = document.querySelectorAll('['+ sessionType + '-visibility]');
     for (var i = 0; i < elements.length; i++) {
       var element = elements[i];
-      var visibility = element.getAttribute(sessionType +'-visibility');
+      var visibility = element.getAttribute(sessionType + '-visibility');
       if (visibility == 'hidden')
         element.hidden = true;
       else if (visibility == 'disabled')
@@ -86,7 +106,7 @@ cr.define('uiAccountTweaks', function() {
    * @param {Document} document Document that should processed.
    */
   UIAccountTweaks.applyGuestSessionVisibility = function(document) {
-    if (!cr.isChromeOS || !UIAccountTweaks.loggedInAsGuest())
+    if (!UIAccountTweaks.loggedInAsGuest())
       return;
     UIAccountTweaks.applySessionTypeVisibility_(document, SESSION_TYPE_GUEST);
   }
@@ -98,7 +118,7 @@ cr.define('uiAccountTweaks', function() {
    * @param {Document} document Document that should processed.
    */
   UIAccountTweaks.applyPublicSessionVisibility = function(document) {
-    if (!cr.isChromeOS || !UIAccountTweaks.loggedInAsPublicAccount())
+    if (!UIAccountTweaks.loggedInAsPublicAccount())
       return;
     UIAccountTweaks.applySessionTypeVisibility_(document, SESSION_TYPE_PUBLIC);
   }