Customize: Allow control subclasses to add to the deferred object before the base class initializes.

Update the `CodeEditorControl`'s `codemirror` deferred to be set before calling the parent class's `initialize` method. Since the `ready` method may be called directly by `initialize` it may be too late to add a new `Deferred` to the control's `deferred` property after calling the base control class's `initialize`.

Amends [41958].
See #41897.

Built from https://develop.svn.wordpress.org/trunk@41960


git-svn-id: http://core.svn.wordpress.org/trunk@41794 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.9-beta3-41959';
+$wp_version = '4.9-beta3-41960';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.