Restore 'insert-media-button' as an ID attribute for the first instance of media_buttons(). Remove IDs for subsequent instances.

props nacin.
fixes #28090.
Built from https://develop.svn.wordpress.org/trunk@29671


git-svn-id: http://core.svn.wordpress.org/trunk@29445 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/edit-form-advanced.php

@@ -504,7 +504,7 @@ if ( post_type_supports($post_type, 'editor') ) {
 <?php wp_editor( $post->post_content, 'content', array(
 	'dfw' => true,
 	'drag_drop_upload' => true,
-	'tabfocus_elements' => 'insert-media-button-1,save-post',
+	'tabfocus_elements' => 'insert-media-button,save-post',
 	'editor_height' => 300,
 	'tinymce' => array(
 		'resize' => false,

wp-admin/includes/media.php

@@ -528,8 +528,9 @@ function media_buttons($editor_id = 'content') {
 
 	$img = '<span class="wp-media-buttons-icon"></span> ';
 
-	printf( '<a href="#" id="insert-media-button-%d" class="button insert-media add_media" data-editor="%s" title="%s">%s</a>',
-		$instance,
+	$id_attribute = $instance === 1 ? ' id="insert-media-button"' : '';
+	printf( '<a href="#"%s class="button insert-media add_media" data-editor="%s" title="%s">%s</a>',
+		$id_attribute,
 		esc_attr( $editor_id ),
 		esc_attr__( 'Add Media' ),
 		$img . __( 'Add Media' )