Disable wallpaper button in Guest mode settings

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

Index: ui/webui/resources/js/chromeos/ui_account_tweaks.js
diff --git a/ui/webui/resources/js/chromeos/ui_account_tweaks.js b/ui/webui/resources/js/chromeos/ui_account_tweaks.js
index 76c2d90d1e93a7a158178ea97fc4135dec19351f..b6fa35d9fdd98584aba6f5aa69543d5aa80a2f0c 100644
--- a/ui/webui/resources/js/chromeos/ui_account_tweaks.js
+++ b/ui/webui/resources/js/chromeos/ui_account_tweaks.js
@@ -57,6 +57,26 @@ cr.define('uiAccountTweaks', function() {
   };
 
   /**
+   * 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') {

[Dan Beam, 2014/09/29 18:52:18]

nit: + '

[michaelpg, 2014/09/29 21:21:58]

Done.

+      return;
+    }
+
+    element.disabled = false;
+  }
+
+  /**
    * Disables or hides some elements in specified type of session in ChromeOS.
    * All elements within given document with *sessionType*-visibility
    * attribute are either hidden (for *sessionType*-visibility="hidden")
@@ -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);
   }