Add a `create_wp_error` action which is called when a `WP_Error` instance is created. Fixes #28319. Props ebinnion

Built from https://develop.svn.wordpress.org/trunk@29033


git-svn-id: http://core.svn.wordpress.org/trunk@28821 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-error.php

@@ -63,6 +63,15 @@ class WP_Error {
 
 		if ( ! empty($data) )
 			$this->error_data[$code] = $data;
+
+		/**
+		 * Fires when a WP_Error object instance is created.
+		 *
+		 * @since 4.0.0
+		 *
+		 * @param WP_Error $this The WP_Error instance.
+		 */
+		do_action( 'create_wp_error', $this );
 	}
 
 	/**