Widgets: Allow relative/partial URLs in Image Widget's link field.

Props audrasjb.
Amends [41252].
See #41274.
Fixes #42740 for 4.9 branch.

Built from https://develop.svn.wordpress.org/branches/4.9@42534


git-svn-id: http://core.svn.wordpress.org/branches/4.9@42363 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.9.3-alpha-42532';
+$wp_version = '4.9.3-alpha-42534';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.

wp-includes/widgets/class-wp-widget-media-image.php

@@ -320,7 +320,7 @@ class WP_Widget_Media_Image extends WP_Widget_Media {
 			<# if ( data.url ) { #>
 			<p class="media-widget-image-link">
 				<label for="{{ elementIdPrefix }}linkUrl"><?php esc_html_e( 'Link to:' ); ?></label>
-				<input id="{{ elementIdPrefix }}linkUrl" type="url" class="widefat link" value="{{ data.link_url }}" placeholder="http://">
+				<input id="{{ elementIdPrefix }}linkUrl" type="text" class="widefat link" value="{{ data.link_url }}" placeholder="http://" pattern="((\w+:)?\/\/\w.*|\w+:(?!\/\/$)|\/|\?|#).*">
 			</p>
 			<# } #>
 		</script>