Index: src/wp-includes/js/tinymce/skins/wordpress/wp-content.css
===================================================================
--- src/wp-includes/js/tinymce/skins/wordpress/wp-content.css	(revision 28963)
+++ src/wp-includes/js/tinymce/skins/wordpress/wp-content.css	(working copy)
@@ -347,6 +347,10 @@
 	color: #2ea2cc;
 }
 
+.wpview-content iframe {
+	display: block;
+}
+
 /* Audio player is short; therefore let's put the toolbar above */
 .wpview-type-audio .toolbar {
 	top: auto;