Index: src/wp-includes/css/media-views.css
===================================================================
--- src/wp-includes/css/media-views.css	(revision 35465)
+++ src/wp-includes/css/media-views.css	(working copy)
@@ -1085,6 +1085,7 @@
 }
 
 .attachments-browser .media-toolbar-secondary {
+	width:100%;
 	max-width: 66%;
 }