Index: src/wp-includes/media.php
===================================================================
--- src/wp-includes/media.php	(revision 34248)
+++ src/wp-includes/media.php	(working copy)
@@ -148,7 +148,7 @@
  * @param int          $id   Attachment ID for image.
  * @param array|string $size Optional. Image size to scale to. Accepts a registered image size
  *                           or flat array of height and width values. Default 'medium'.
- * @return false|array False on failure, array on success.
+ * @return false|array False on failure, array (url, width, height, is_intermediate) on success.
  */
 function image_downsize( $id, $size = 'medium' ) {
 
@@ -691,6 +691,11 @@
  *
  * A mime icon for files, thumbnail or intermediate size for images.
  *
+ * The returned array contains four values: the URL of the attachment image src,
+ * the width of the image file, the height of the image file, and a boolean
+ * representing whether the returned array describes an intermediate (generated)
+ * image size or the original, full-sized upload.
+ *
  * @since 2.5.0
  *
  * @param int          $attachment_id Image attachment ID.
@@ -697,7 +702,7 @@
  * @param string|array $size          Optional. Registered image size to retrieve the source for or a flat
  *                                    array of height and width dimensions. Default 'thumbnail'.
  * @param bool         $icon          Optional. Whether the image should be treated as an icon. Default false.
- * @return false|array Returns an array (url, width, height), or false, if no image is available.
+ * @return false|array Returns an array (url, width, height, is_intermediate), or false, if no image is available.
  */
 function wp_get_attachment_image_src( $attachment_id, $size = 'thumbnail', $icon = false ) {
 	// get a thumbnail or intermediate image if there is one