Index: wp-admin/css/common.css
===================================================================
--- wp-admin/css/common.css	(revision 40352)
+++ wp-admin/css/common.css	(working copy)
@@ -1161,6 +1161,10 @@
 	display: block;
 	overflow: hidden;
 	width: 100%;
+	-webkit-box-sizing: border-box;
+    -moz-box-sizing: border-box;
+    box-sizing: border-box;
+	margin: 0;
 }
 
 .show-filters .filter-links a.current {