Disable chrome://options UI elements if the corresponding preference is not user-modifiable.

chrome/browser/resources/options/pref_ui.js

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 cr.define('options', function() {
 
   var Preferences = options.Preferences;
 
   /**
    * Helper function update element's state from pref change event.
    * @private
    * @param {!HTMLElement} el The element to update.
    * @param {!Event} event The pref change event.
    */
   function updateElementState_(el, event) {
-    el.managed = event.value && event.value['managed'] != undefined ?
-        event.value['managed'] : false;
+    el.managed = false;
 
-    // Managed UI elements can only be disabled as a result of being
-    // managed. They cannot be enabled as a result of a pref being
-    // unmanaged.
-    if (el.managed)
-      el.disabled = true;
+    if (!event.value)
+      return;
+
+    el.managed = event.value['managed'];
+
+    if (event.value['extensionControlled']) {
+      // Set an explanatory title attribute on the nearest containing <label>
+      // element.
+      var node = el;
+      while (node) {

[Evan Stade, 2011/07/06 19:44:57]

use findAncestor from util.js

[Bernhard Bauer, 2011/07/06 19:55:57]

Ahh, nice. Done.

+        if (node instanceof HTMLLabelElement) {
+          node.title = templateData.extensionManagedPrefsTitle;
+          break;
+        }
+        node = node.parentNode;
+      }
+    }
 
     // Disable UI elements if backend says so.
-    if (!el.disabled && event.value && event.value['disabled'])
+    if (event.value['disabled'])
       el.disabled = true;

[Evan Stade, 2011/07/06 19:44:57]

does this work?

el.disabled = event.value['disabled']

[Bernhard Bauer, 2011/07/06 19:55:57]

I think elements could already be disabled for other reasons, and we wouldn't
want to enable them in that case. 

[Evan Stade, 2011/07/06 20:12:43]

true, but what if a user uninstalls an extension -- shouldn't this go back to
false? (and shouldn't the label title go back to empty)

[Bernhard Bauer, 2011/07/07 08:45:56]

Done.

   }
 
   /////////////////////////////////////////////////////////////////////////////
   // PrefCheckbox class:
   // TODO(jhawkins): Refactor all this copy-pasted code!
 
   // Define a constructor that uses an input element as its underlying element.
   var PrefCheckbox = cr.ui.define('input');
 
   PrefCheckbox.prototype = {
@@ skipping 483 matching lines @@
     PrefCheckbox: PrefCheckbox,
     PrefNumber: PrefNumber,
     PrefNumeric: PrefNumeric,
     PrefRadio: PrefRadio,
     PrefRange: PrefRange,
     PrefSelect: PrefSelect,
     PrefTextField: PrefTextField
   };
 
 });