Accessibility: Add a default title for the media modal dialog.

Makes sure the media modal dialog `h1` heading isn't empty when custom media frames don't set a title. This is particularly important now that the media modal is an ARIA dialog, as the title is referenced by an `aria-labelledby` attribute to properly label the dialog.

Props donmhico, audrasjb.
Fixes #47612.


git-svn-id: https://develop.svn.wordpress.org/trunk@45925 602fd350-edb4-49c9-b593-d223f7449a82

src/js/media/views/media-frame.js

@@ -1,4 +1,5 @@
 var Frame = wp.media.view.Frame,
+	l10n = wp.media.view.l10n,
 	$ = jQuery,
 	MediaFrame;
 
@@ -32,7 +33,7 @@ MediaFrame = Frame.extend(/** @lends wp.media.view.MediaFrame.prototype */{
 		Frame.prototype.initialize.apply( this, arguments );
 
 		_.defaults( this.options, {
-			title:    '',
+			title:    l10n.mediaFrameDefaultTitle,
 			modal:    true,
 			uploader: true
 		});

src/wp-includes/media.php

@@ -3764,6 +3764,7 @@ function wp_enqueue_media( $args = array() ) {
 
 	$strings = array(
 		// Generic
+		'mediaFrameDefaultTitle'      => __( 'Media' ),
 		'url'                         => __( 'URL' ),
 		'addMedia'                    => __( 'Add Media' ),
 		'search'                      => __( 'Search' ),