Embeds: URL encode YouTube video IDs for broader compatibility.

Merge of [40160] to the 4.1 branch.

Built from https://develop.svn.wordpress.org/branches/4.1@40167


git-svn-id: http://core.svn.wordpress.org/branches/4.1@40106 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/media.php

@@ -2297,7 +2297,7 @@ function wp_embed_handler_googlevideo( $matches, $attr, $url, $rawattr ) {
  */
 function wp_embed_handler_youtube( $matches, $attr, $url, $rawattr ) {
 	global $wp_embed;
-	$embed = $wp_embed->autoembed( "https://youtube.com/watch?v={$matches[2]}" );
+	$embed = $wp_embed->autoembed( sprintf( "https://youtube.com/watch?v=%s", urlencode( $matches[2] ) ) );
 	/**
 	 * Filter the YoutTube embed output.
 	 *