Index: src/wp-includes/media.php
===================================================================
--- src/wp-includes/media.php	(revision 35695)
+++ src/wp-includes/media.php	(working copy)
@@ -1065,6 +1065,10 @@
 				'url'        => $image_baseurl . $image['file'],
 				'descriptor' => 'w',
 				'value'      => $image['width'],
+				'size'       => array(
+					'width'  => $image['width'],
+					'height' => $image['height'],
+					),
 			);
 		}
 	}
@@ -1083,6 +1087,10 @@
 	 *                                        either 'w' or 'x'.
 	 *          @type type int    $value      The source width, if paired with a 'w' descriptor or a
 	 *                                        pixel density value if paired with an 'x' descriptor.
+	 *          @type type array  $sizes {
+	 *                @type int $width  Width of the source image.
+	 *                @type int $height Height of the source image.
+	 *                }
 	 *     }
 	 * }
 	 * @param array  $size_array    Array of width and height values in pixels (in that order).