Responsive images: do not generate `srcset` for GIFs that are inserted at full size. Prevents breaking animated GIFs.

Props joemcgill.
Fixes #34528.
Built from https://develop.svn.wordpress.org/trunk@35524


git-svn-id: http://core.svn.wordpress.org/trunk@35488 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/media.php

@@ -983,6 +983,13 @@ function wp_calculate_image_srcset( $image_src, $size_array, $image_meta, $attac
 		return false;
 	}
 
+	// Don't add srcset attributes to (animated) gifs that are inserted at full size.
+	if ( isset( $image_sizes['thumbnail']['mime-type'] ) && 'image/gif' === $image_sizes['thumbnail']['mime-type'] &&
+		false !== strpos( $image_src, $image_meta['file'] ) ) {
+
+		return false;
+	}
+
 	$image_basename = wp_basename( $image_meta['file'] );
 	$image_baseurl = _wp_upload_dir_baseurl();
 

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.4-beta2-35523';
+$wp_version = '4.4-beta2-35524';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.