Index: wp-admin/includes/class-wp-ms-sites-list-table.php
===================================================================
--- wp-admin/includes/class-wp-ms-sites-list-table.php	(revision 21813)
+++ wp-admin/includes/class-wp-ms-sites-list-table.php	(working copy)
@@ -9,9 +9,10 @@
  */
 class WP_MS_Sites_List_Table extends WP_List_Table {
 
-	function __construct() {
+	function __construct( $args = array() ) {
 		parent::__construct( array(
 			'plural' => 'sites',
+			'screen' => isset( $args['screen'] ) ? $args['screen'] : null,
 		) );
 	}
 
Index: wp-admin/includes/class-wp-posts-list-table.php
===================================================================
--- wp-admin/includes/class-wp-posts-list-table.php	(revision 21813)
+++ wp-admin/includes/class-wp-posts-list-table.php	(working copy)
@@ -45,10 +45,15 @@
 	 */
 	var $sticky_posts_count = 0;
 
-	function __construct() {
+	function __construct( $args = array() ) {
 		global $post_type_object, $wpdb;
 
-		$post_type = get_current_screen()->post_type;
+		parent::__construct( array(
+			'plural' => 'posts',
+			'screen' => isset( $args['screen'] ) ? $args['screen'] : null,
+		) );
+
+		$post_type = $this->screen->post_type;
 		$post_type_object = get_post_type_object( $post_type );
 
 		if ( !current_user_can( $post_type_object->cap->edit_others_posts ) ) {
@@ -66,28 +71,22 @@
 			$sticky_posts = implode( ', ', array_map( 'absint', (array) $sticky_posts ) );
 			$this->sticky_posts_count = $wpdb->get_var( $wpdb->prepare( "SELECT COUNT( 1 ) FROM $wpdb->posts WHERE post_type = %s AND post_status != 'trash' AND ID IN ($sticky_posts)", $post_type ) );
 		}
-
-		parent::__construct( array(
-			'plural' => 'posts',
-		) );
 	}
 
 	function ajax_user_can() {
-		global $post_type_object;
-
-		return current_user_can( $post_type_object->cap->edit_posts );
+		return current_user_can( get_post_type_object( $this->screen->post_type )->cap->edit_posts );
 	}
 
 	function prepare_items() {
-		global $post_type_object, $avail_post_stati, $wp_query, $per_page, $mode;
+		global $avail_post_stati, $wp_query, $per_page, $mode;
 
 		$avail_post_stati = wp_edit_posts_query();
 
-		$this->hierarchical_display = ( $post_type_object->hierarchical && 'menu_order title' == $wp_query->query['orderby'] );
+		$this->hierarchical_display = ( is_post_type_hierarchical( $this->screen->post_type ) && 'menu_order title' == $wp_query->query['orderby'] );
 
 		$total_items = $this->hierarchical_display ? $wp_query->post_count : $wp_query->found_posts;
 
-		$post_type = $post_type_object->name;
+		$post_type = $this->screen->post_type;
 		$per_page = $this->get_items_per_page( 'edit_' . $post_type . '_per_page' );
  		$per_page = apply_filters( 'edit_posts_per_page', $per_page, $post_type );
 
@@ -112,18 +111,16 @@
 	}
 
 	function no_items() {
-		global $post_type_object;
-
 		if ( isset( $_REQUEST['post_status'] ) && 'trash' == $_REQUEST['post_status'] )
-			echo $post_type_object->labels->not_found_in_trash;
+			echo get_post_type_object( $this->screen->post_type )->labels->not_found_in_trash;
 		else
-			echo $post_type_object->labels->not_found;
+			echo get_post_type_object( $this->screen->post_type )->labels->not_found;
 	}
 
 	function get_views() {
-		global $post_type_object, $locked_post_status, $avail_post_stati;
+		global $locked_post_status, $avail_post_stati;
 
-		$post_type = $post_type_object->name;
+		$post_type = $this->screen->post_type;
 
 		if ( !empty($locked_post_status) )
 			return array();
@@ -198,15 +195,15 @@
 	}
 
 	function extra_tablenav( $which ) {
-		global $post_type_object, $cat;
+		global $cat;
 ?>
 		<div class="alignleft actions">
 <?php
 		if ( 'top' == $which && !is_singular() ) {
 
-			$this->months_dropdown( $post_type_object->name );
+			$this->months_dropdown( $this->screen->post_type );
 
-			if ( is_object_in_taxonomy( $post_type_object->name, 'category' ) ) {
+			if ( is_object_in_taxonomy( $this->screen->post_type, 'category' ) ) {
 				$dropdown_options = array(
 					'show_option_all' => __( 'View all categories' ),
 					'hide_empty' => 0,
@@ -221,7 +218,7 @@
 			submit_button( __( 'Filter' ), 'small', false, false, array( 'id' => 'post-query-submit' ) );
 		}
 
-		if ( $this->is_trash && current_user_can( $post_type_object->cap->edit_others_posts ) ) {
+		if ( $this->is_trash && current_user_can( get_post_type_object( $this->screen->post_type )->cap->edit_others_posts ) ) {
 			submit_button( __( 'Empty Trash' ), 'small apply', 'delete_all', false );
 		}
 ?>
@@ -237,28 +234,21 @@
 	}
 
 	function pagination( $which ) {
-		global $post_type_object, $mode;
+		global $mode;
 
 		parent::pagination( $which );
 
-		if ( 'top' == $which && !$post_type_object->hierarchical )
+		if ( 'top' == $which && ! is_post_type_hierarchical( $this->screen->post_type ) )
 			$this->view_switcher( $mode );
 	}
 
 	function get_table_classes() {
-		global $post_type_object;
-
-		return array( 'widefat', 'fixed', $post_type_object->hierarchical ? 'pages' : 'posts' );
+		return array( 'widefat', 'fixed', is_post_type_hierarchical( $this->screen->post_type ) ? 'pages' : 'posts' );
 	}
 
 	function get_columns() {
-		$screen = get_current_screen();
+		$post_type = $this->screen->post_type;
 
-		if ( empty( $screen ) )
-			$post_type = 'post';
-		else
-			$post_type = $screen->post_type;
-
 		$posts_columns = array();
 
 		$posts_columns['cb'] = '<input type="checkbox" />';
@@ -313,7 +303,7 @@
 	}
 
 	function display_rows( $posts = array(), $level = 0 ) {
-		global $wp_query, $post_type_object, $per_page;
+		global $wp_query, $per_page;
 
 		if ( empty( $posts ) )
 			$posts = $wp_query->posts;
@@ -701,12 +691,10 @@
 	function inline_edit() {
 		global $mode;
 
-		$screen = get_current_screen();
+		$post = get_default_post_to_edit( $this->screen->post_type );
+		$post_type_object = get_post_type_object( $this->screen->post_type );
 
-		$post = get_default_post_to_edit( $screen->post_type );
-		$post_type_object = get_post_type_object( $screen->post_type );
-
-		$taxonomy_names = get_object_taxonomies( $screen->post_type );
+		$taxonomy_names = get_object_taxonomies( $this->screen->post_type );
 		$hierarchical_taxonomies = array();
 		$flat_taxonomies = array();
 		foreach ( $taxonomy_names as $taxonomy_name ) {
@@ -733,15 +721,15 @@
 		$bulk = 0;
 		while ( $bulk < 2 ) { ?>
 
-		<tr id="<?php echo $bulk ? 'bulk-edit' : 'inline-edit'; ?>" class="inline-edit-row inline-edit-row-<?php echo "$hclass inline-edit-$screen->post_type ";
-			echo $bulk ? "bulk-edit-row bulk-edit-row-$hclass bulk-edit-$screen->post_type" : "quick-edit-row quick-edit-row-$hclass inline-edit-$screen->post_type";
+		<tr id="<?php echo $bulk ? 'bulk-edit' : 'inline-edit'; ?>" class="inline-edit-row inline-edit-row-<?php echo "$hclass inline-edit-" . $this->screen->post_type;
+			echo $bulk ? "bulk-edit-row bulk-edit-row-$hclass bulk-edit-" . $this->screen->post_type : "quick-edit-row quick-edit-row-$hclass inline-edit-" . $this->screen->post_type;
 		?>" style="display: none"><td colspan="<?php echo $this->get_column_count(); ?>" class="colspanchange">
 
 		<fieldset class="inline-edit-col-left"><div class="inline-edit-col">
 			<h4><?php echo $bulk ? __( 'Bulk Edit' ) : __( 'Quick Edit' ); ?></h4>
 	<?php
 
-	if ( post_type_supports( $screen->post_type, 'title' ) ) :
+	if ( post_type_supports( $this->screen->post_type, 'title' ) ) :
 		if ( $bulk ) : ?>
 			<div id="bulk-title-div">
 				<div id="bulk-titles"></div>
@@ -770,7 +758,7 @@
 			<br class="clear" />
 	<?php endif; // $bulk
 
-		if ( post_type_supports( $screen->post_type, 'author' ) ) :
+		if ( post_type_supports( $this->screen->post_type, 'author' ) ) :
 			$authors_dropdown = '';
 
 			if ( is_super_admin() || current_user_can( $post_type_object->cap->edit_others_posts ) ) :
@@ -846,10 +834,10 @@
 		<fieldset class="inline-edit-col-right"><div class="inline-edit-col">
 
 	<?php
-		if ( post_type_supports( $screen->post_type, 'author' ) && $bulk )
+		if ( post_type_supports( $this->screen->post_type, 'author' ) && $bulk )
 			echo $authors_dropdown;
 
-		if ( post_type_supports( $screen->post_type, 'page-attributes' ) ) :
+		if ( post_type_supports( $this->screen->post_type, 'page-attributes' ) ) :
 
 			if ( $post_type_object->hierarchical ) :
 		?>
@@ -884,7 +872,7 @@
 
 	<?php	endif; // !$bulk
 
-			if ( 'page' == $screen->post_type ) :
+			if ( 'page' == $this->screen->post_type ) :
 	?>
 
 			<label>
@@ -917,11 +905,11 @@
 
 	<?php endif; // count( $flat_taxonomies ) && !$bulk  ?>
 
-	<?php if ( post_type_supports( $screen->post_type, 'comments' ) || post_type_supports( $screen->post_type, 'trackbacks' ) ) :
+	<?php if ( post_type_supports( $this->screen->post_type, 'comments' ) || post_type_supports( $this->screen->post_type, 'trackbacks' ) ) :
 		if ( $bulk ) : ?>
 
 			<div class="inline-edit-group">
-		<?php if ( post_type_supports( $screen->post_type, 'comments' ) ) : ?>
+		<?php if ( post_type_supports( $this->screen->post_type, 'comments' ) ) : ?>
 			<label class="alignleft">
 				<span class="title"><?php _e( 'Comments' ); ?></span>
 				<select name="comment_status">
@@ -930,7 +918,7 @@
 					<option value="closed"><?php _e( 'Do not allow' ); ?></option>
 				</select>
 			</label>
-		<?php endif; if ( post_type_supports( $screen->post_type, 'trackbacks' ) ) : ?>
+		<?php endif; if ( post_type_supports( $this->screen->post_type, 'trackbacks' ) ) : ?>
 			<label class="alignright">
 				<span class="title"><?php _e( 'Pings' ); ?></span>
 				<select name="ping_status">
@@ -945,12 +933,12 @@
 	<?php else : // $bulk ?>
 
 			<div class="inline-edit-group">
-			<?php if ( post_type_supports( $screen->post_type, 'comments' ) ) : ?>
+			<?php if ( post_type_supports( $this->screen->post_type, 'comments' ) ) : ?>
 				<label class="alignleft">
 					<input type="checkbox" name="comment_status" value="open" />
 					<span class="checkbox-title"><?php _e( 'Allow Comments' ); ?></span>
 				</label>
-			<?php endif; if ( post_type_supports( $screen->post_type, 'trackbacks' ) ) : ?>
+			<?php endif; if ( post_type_supports( $this->screen->post_type, 'trackbacks' ) ) : ?>
 				<label class="alignleft">
 					<input type="checkbox" name="ping_status" value="open" />
 					<span class="checkbox-title"><?php _e( 'Allow Pings' ); ?></span>
@@ -980,7 +968,7 @@
 					</select>
 				</label>
 
-	<?php if ( 'post' == $screen->post_type && $can_publish && current_user_can( $post_type_object->cap->edit_others_posts ) ) : ?>
+	<?php if ( 'post' == $this->screen->post_type && $can_publish && current_user_can( $post_type_object->cap->edit_others_posts ) ) : ?>
 
 	<?php	if ( $bulk ) : ?>
 
@@ -1006,7 +994,7 @@
 
 			</div>
 
-	<?php if ( post_type_supports( $screen->post_type, 'post-formats' ) && current_theme_supports( 'post-formats' ) ) :
+	<?php if ( post_type_supports( $this->screen->post_type, 'post-formats' ) && current_theme_supports( 'post-formats' ) ) :
 		$post_formats = get_theme_support( 'post-formats' );
 		if ( isset( $post_formats[0] ) && is_array( $post_formats[0] ) ) :
 			$all_post_formats = get_post_format_strings();
@@ -1039,7 +1027,7 @@
 		foreach ( $columns as $column_name => $column_display_name ) {
 			if ( isset( $core_columns[$column_name] ) )
 				continue;
-			do_action( $bulk ? 'bulk_edit_custom_box' : 'quick_edit_custom_box', $column_name, $screen->post_type );
+			do_action( $bulk ? 'bulk_edit_custom_box' : 'quick_edit_custom_box', $column_name, $this->screen->post_type );
 		}
 	?>
 		<p class="submit inline-edit-save">
@@ -1054,7 +1042,7 @@
 				submit_button( __( 'Update' ), 'button-primary alignright', 'bulk_edit', false, array( 'accesskey' => 's' ) );
 			} ?>
 			<input type="hidden" name="post_view" value="<?php echo esc_attr( $m ); ?>" />
-			<input type="hidden" name="screen" value="<?php echo esc_attr( $screen->id ); ?>" />
+			<input type="hidden" name="screen" value="<?php echo esc_attr( $this->screen->id ); ?>" />
 			<span class="error" style="display:none"></span>
 			<br class="clear" />
 		</p>
Index: wp-admin/includes/list-table.php
===================================================================
--- wp-admin/includes/list-table.php	(revision 21813)
+++ wp-admin/includes/list-table.php	(working copy)
@@ -14,9 +14,10 @@
  * @since 3.1.0
  *
  * @param string $class The type of the list table, which is the class name.
+ * @param array $args Optional. Arguments to pass to the class. Accepts 'screen'.
  * @return object|bool Object on success, false if the class does not exist.
  */
-function _get_list_table( $class ) {
+function _get_list_table( $class, $args = array() ) {
 	$core_classes = array(
 		//Site Admin
 		'WP_Posts_List_Table' => 'posts',
@@ -39,7 +40,13 @@
 	if ( isset( $core_classes[ $class ] ) ) {
 		foreach ( (array) $core_classes[ $class ] as $required )
 			require_once( ABSPATH . 'wp-admin/includes/class-wp-' . $required . '-list-table.php' );
-		return new $class;
+
+		if ( isset( $args['screen'] ) )
+			$args['screen'] = convert_to_screen( $args['screen'] );
+		else
+			$args['screen'] = get_current_screen();
+
+		return new $class( $args );
 	}
 
 	return false;
Index: wp-admin/includes/class-wp-media-list-table.php
===================================================================
--- wp-admin/includes/class-wp-media-list-table.php	(revision 21813)
+++ wp-admin/includes/class-wp-media-list-table.php	(working copy)
@@ -9,11 +9,12 @@
  */
 class WP_Media_List_Table extends WP_List_Table {
 
-	function __construct() {
+	function __construct( $args = array() ) {
 		$this->detached = isset( $_REQUEST['detached'] ) || isset( $_REQUEST['find_detached'] );
 
 		parent::__construct( array(
-			'plural' => 'media'
+			'plural' => 'media',
+			'screen' => isset( $args['screen'] ) ? $args['screen'] : null,
 		) );
 	}
 
Index: wp-admin/includes/class-wp-links-list-table.php
===================================================================
--- wp-admin/includes/class-wp-links-list-table.php	(revision 21813)
+++ wp-admin/includes/class-wp-links-list-table.php	(working copy)
@@ -9,9 +9,10 @@
  */
 class WP_Links_List_Table extends WP_List_Table {
 
-	function __construct() {
+	function __construct( $args = array() ) {
 		parent::__construct( array(
 			'plural' => 'bookmarks',
+			'screen' => isset( $args['screen'] ) ? $args['screen'] : null,
 		) );
 	}
 
Index: wp-admin/includes/class-wp-terms-list-table.php
===================================================================
--- wp-admin/includes/class-wp-terms-list-table.php	(revision 21813)
+++ wp-admin/includes/class-wp-terms-list-table.php	(working copy)
@@ -11,43 +11,46 @@
 
 	var $callback_args;
 
-	function __construct() {
-		global $post_type, $taxonomy, $tax;
+	function __construct( $args = array() ) {
+		global $post_type, $taxonomy, $action, $tax;
 
-		wp_reset_vars( array( 'action', 'taxonomy', 'post_type' ) );
+		parent::__construct( array(
+			'plural' => 'tags',
+			'singular' => 'tag',
+			'screen' => isset( $args['screen'] ) ? $args['screen'] : null,
+		) );
 
+		$action    = $this->screen->action;
+		$post_type = $this->screen->post_type;
+		$taxonomy  = $this->screen->taxonomy;
+
+		// @todo Still needed? Not sure if WP_Screen allows 'taxonomy' to be empty.
 		if ( empty( $taxonomy ) )
 			$taxonomy = 'post_tag';
 
-		if ( !taxonomy_exists( $taxonomy ) )
+		// @todo Still needed? Not sure if WP_Screen allows for 'taxonomy' to be invalid.
+		if ( ! taxonomy_exists( $taxonomy ) )
 			wp_die( __( 'Invalid taxonomy' ) );
 
 		$tax = get_taxonomy( $taxonomy );
 
+		// @todo Still needed? Maybe just the show_ui part.
 		if ( empty( $post_type ) || !in_array( $post_type, get_post_types( array( 'show_ui' => true ) ) ) )
 			$post_type = 'post';
 
-		parent::__construct( array(
-			'plural' => 'tags',
-			'singular' => 'tag',
-		) );
 	}
 
 	function ajax_user_can() {
-		global $tax;
-
-		return current_user_can( $tax->cap->manage_terms );
+		return current_user_can( get_taxonomy( $this->screen->taxonomy )->cap->manage_terms );
 	}
 
 	function prepare_items() {
-		global $taxonomy;
+		$tags_per_page = $this->get_items_per_page( 'edit_' . $this->screen->taxonomy . '_per_page' );
 
-		$tags_per_page = $this->get_items_per_page( 'edit_' . $taxonomy . '_per_page' );
-
-		if ( 'post_tag' == $taxonomy ) {
+		if ( 'post_tag' == $this->screen->taxonomy ) {
 			$tags_per_page = apply_filters( 'edit_tags_per_page', $tags_per_page );
 			$tags_per_page = apply_filters( 'tagsperpage', $tags_per_page ); // Old filter
-		} elseif ( 'category' == $taxonomy ) {
+		} elseif ( 'category' == $this->screen->taxonomy ) {
 			$tags_per_page = apply_filters( 'edit_categories_per_page', $tags_per_page ); // Old filter
 		}
 
@@ -68,7 +71,7 @@
 		$this->callback_args = $args;
 
 		$this->set_pagination_args( array(
-			'total_items' => wp_count_terms( $taxonomy, compact( 'search' ) ),
+			'total_items' => wp_count_terms( $this->screen->taxonomy, compact( 'search' ) ),
 			'per_page' => $tags_per_page,
 		) );
 	}
@@ -93,8 +96,6 @@
 	}
 
 	function get_columns() {
-		global $taxonomy, $post_type;
-
 		$columns = array(
 			'cb'          => '<input type="checkbox" />',
 			'name'        => _x( 'Name', 'term name' ),
@@ -102,10 +103,10 @@
 			'slug'        => __( 'Slug' ),
 		);
 
-		if ( 'link_category' == $taxonomy ) {
+		if ( 'link_category' == $this->screen->taxonomy ) {
 			$columns['links'] = __( 'Links' );
 		} else {
-			$post_type_object = get_post_type_object( $post_type );
+			$post_type_object = get_post_type_object( $this->screen->post_type );
 			$columns['posts'] = $post_type_object ? $post_type_object->labels->name : __( 'Posts' );
 		}
 
@@ -123,7 +124,7 @@
 	}
 
 	function display_rows_or_placeholder() {
-		global $taxonomy;
+		$taxonomy = $this->screen->taxonomy;
 
 		$args = wp_parse_args( $this->callback_args, array(
 			'page' => 1,
@@ -231,11 +232,9 @@
 	}
 
 	function column_cb( $tag ) {
-		global $taxonomy, $tax;
+		$default_term = get_option( 'default_' . $this->screen->taxonomy );
 
-		$default_term = get_option( 'default_' . $taxonomy );
-
-		if ( current_user_can( $tax->cap->delete_terms ) && $tag->term_id != $default_term )
+		if ( current_user_can( get_taxonomy( $this->screen->taxonomy )->cap->delete_terms ) && $tag->term_id != $default_term )
 			return '<label class="screen-reader-text" for="cb-select-' . $tag->term_id . '">' . sprintf( __( 'Select %s' ), $tag->name ) . '</label>'
 				. '<input type="checkbox" name="delete_tags[]" value="' . $tag->term_id . '" id="cb-select-' . $tag->term_id . '" />';
 
@@ -243,14 +242,15 @@
 	}
 
 	function column_name( $tag ) {
-		global $taxonomy, $tax, $post_type;
+		$taxonomy = $this->screen->taxonomy;
+		$tax = get_taxonomy( $taxonomy );
 
 		$default_term = get_option( 'default_' . $taxonomy );
 
 		$pad = str_repeat( '&#8212; ', max( 0, $this->level ) );
 		$name = apply_filters( 'term_name', $pad . ' ' . $tag->name, $tag );
 		$qe_data = get_term( $tag->term_id, $taxonomy, OBJECT, 'edit' );
-		$edit_link = esc_url( get_edit_term_link( $tag->term_id, $taxonomy, $post_type ) );
+		$edit_link = esc_url( get_edit_term_link( $tag->term_id, $taxonomy, $this->screen->post_type ) );
 
 		$out = '<strong><a class="row-title" href="' . $edit_link . '" title="' . esc_attr( sprintf( __( 'Edit &#8220;%s&#8221;' ), $name ) ) . '">' . $name . '</a></strong><br />';
 
@@ -284,13 +284,11 @@
 	}
 
 	function column_posts( $tag ) {
-		global $taxonomy, $post_type;
-
 		$count = number_format_i18n( $tag->count );
 
-		$tax = get_taxonomy( $taxonomy );
+		$tax = get_taxonomy( $this->screen->taxonomy );
 
-		$ptype_object = get_post_type_object( $post_type );
+		$ptype_object = get_post_type_object( $this->screen->post_type );
 		if ( ! $ptype_object->show_ui )
 			return $count;
 
@@ -300,8 +298,8 @@
 			$args = array( 'taxonomy' => $tax->name, 'term' => $tag->slug );
 		}
 
-		if ( 'post' != $post_type )
-			$args['post_type'] = $post_type;
+		if ( 'post' != $this->screen->post_type )
+			$args['post_type'] = $this->screen->post_type;
 
 		return "<a href='" . esc_url ( add_query_arg( $args, 'edit.php' ) ) . "'>$count</a>";
 	}
@@ -314,9 +312,7 @@
 	}
 
 	function column_default( $tag, $column_name ) {
-		$screen = get_current_screen();
-
-		return apply_filters( "manage_{$screen->taxonomy}_custom_column", '', $column_name, $tag->term_id );
+		return apply_filters( "manage_{$this->screen->taxonomy}_custom_column", '', $column_name, $tag->term_id );
 	}
 
 	/**
@@ -325,7 +321,7 @@
 	 * @since 3.1.0
 	 */
 	function inline_edit() {
-		global $post_type, $tax;
+		$tax = get_taxonomy( $this->screen->taxonomy );
 
 		if ( ! current_user_can( $tax->cap->edit_terms ) )
 			return;
@@ -358,7 +354,7 @@
 			if ( isset( $core_columns[$column_name] ) )
 				continue;
 
-			do_action( 'quick_edit_custom_box', $column_name, 'edit-tags', $tax->name );
+			do_action( 'quick_edit_custom_box', $column_name, 'edit-tags', $this->screen->taxonomy );
 		}
 
 	?>
@@ -370,8 +366,8 @@
 			<img class="waiting" style="display:none;" src="<?php echo esc_url( admin_url( 'images/wpspin_light.gif' ) ); ?>" alt="" />
 			<span class="error" style="display:none;"></span>
 			<?php wp_nonce_field( 'taxinlineeditnonce', '_inline_edit', false ); ?>
-			<input type="hidden" name="taxonomy" value="<?php echo esc_attr( $tax->name ); ?>" />
-			<input type="hidden" name="post_type" value="<?php echo esc_attr( $post_type ); ?>" />
+			<input type="hidden" name="taxonomy" value="<?php echo esc_attr( $this->screen->taxonomy ); ?>" />
+			<input type="hidden" name="post_type" value="<?php echo esc_attr( $this->screen->post_type ); ?>" />
 			<br class="clear" />
 		</p>
 		</td></tr>
Index: wp-admin/includes/ajax-actions.php
===================================================================
--- wp-admin/includes/ajax-actions.php	(revision 21813)
+++ wp-admin/includes/ajax-actions.php	(working copy)
@@ -29,17 +29,12 @@
  * GET-based Ajax handlers.
  */
 function wp_ajax_fetch_list() {
-	global $current_screen, $wp_list_table;
+	global $wp_list_table;
 
 	$list_class = $_GET['list_args']['class'];
 	check_ajax_referer( "fetch-list-$list_class", '_ajax_fetch_list_nonce' );
 
-	$current_screen = convert_to_screen( $_GET['list_args']['screen']['id'] );
-
-	define( 'WP_NETWORK_ADMIN', $current_screen->is_network );
-	define( 'WP_USER_ADMIN', $current_screen->is_user );
-
-	$wp_list_table = _get_list_table( $list_class );
+	$wp_list_table = _get_list_table( $list_class, array( 'screen' => $_GET['list_args']['screen']['id'] ) );
 	if ( ! $wp_list_table )
 		wp_die( 0 );
 
@@ -615,10 +610,8 @@
 		$x->send();
 	}
 
-	set_current_screen( $_POST['screen'] );
+	$wp_list_table = _get_list_table( 'WP_Terms_List_Table', array( 'screen' => $_POST['screen'] ) );
 
-	$wp_list_table = _get_list_table('WP_Terms_List_Table');
-
 	$level = 0;
 	if ( is_taxonomy_hierarchical($taxonomy) ) {
 		$level = count( get_ancestors( $tag->term_id, $taxonomy ) );
@@ -686,10 +679,8 @@
 
 	check_ajax_referer( $action );
 
-	set_current_screen( 'edit-comments' );
+	$wp_list_table = _get_list_table( 'WP_Post_Comments_List_Table', array( 'screen' => 'edit-comments' ) );
 
-	$wp_list_table = _get_list_table('WP_Post_Comments_List_Table');
-
 	if ( !current_user_can( 'edit_post', $post_id ) )
 		wp_die( -1 );
 
@@ -723,8 +714,6 @@
 
 	check_ajax_referer( $action, '_ajax_nonce-replyto-comment' );
 
-	set_current_screen( 'edit-comments' );
-
 	$comment_post_ID = (int) $_POST['comment_post_ID'];
 	if ( !current_user_can( 'edit_post', $comment_post_ID ) )
 		wp_die( -1 );
@@ -782,9 +771,9 @@
 			_wp_dashboard_recent_comments_row( $comment );
 		} else {
 			if ( 'single' == $_REQUEST['mode'] ) {
-				$wp_list_table = _get_list_table('WP_Post_Comments_List_Table');
+				$wp_list_table = _get_list_table('WP_Post_Comments_List_Table', array( 'screen' => 'edit-comments' ) );
 			} else {
-				$wp_list_table = _get_list_table('WP_Comments_List_Table');
+				$wp_list_table = _get_list_table('WP_Comments_List_Table', array( 'screen' => 'edit-comments' ) );
 			}
 			$wp_list_table->single_row( $comment );
 		}
@@ -811,8 +800,6 @@
 
 	check_ajax_referer( 'replyto-comment', '_ajax_nonce-replyto-comment' );
 
-	set_current_screen( 'edit-comments' );
-
 	$comment_id = (int) $_POST['comment_ID'];
 	if ( ! current_user_can( 'edit_comment', $comment_id ) )
 		wp_die( -1 );
@@ -827,7 +814,7 @@
 	$comments_status = isset($_POST['comments_listing']) ? $_POST['comments_listing'] : '';
 
 	$checkbox = ( isset($_POST['checkbox']) && true == $_POST['checkbox'] ) ? 1 : 0;
-	$wp_list_table = _get_list_table( $checkbox ? 'WP_Comments_List_Table' : 'WP_Post_Comments_List_Table' );
+	$wp_list_table = _get_list_table( $checkbox ? 'WP_Comments_List_Table' : 'WP_Post_Comments_List_Table', array( 'screen' => 'edit-comments' ) );
 
 	$comment = get_comment( $comment_id );
 
@@ -1328,8 +1315,6 @@
 			wp_die( __( 'You are not allowed to edit this post.' ) );
 	}
 
-	set_current_screen( $_POST['screen'] );
-
 	if ( $last = wp_check_post_lock( $post_ID ) ) {
 		$last_user = get_userdata( $last );
 		$last_user_name = $last_user ? $last_user->display_name : __( 'Someone' );
@@ -1365,7 +1350,7 @@
 	// update the post
 	edit_post();
 
-	$wp_list_table = _get_list_table('WP_Posts_List_Table');
+	$wp_list_table = _get_list_table( 'WP_Posts_List_Table', array( 'screen' => $_POST['screen'] ) );
 
 	$mode = $_POST['post_view'];
 
@@ -1397,10 +1382,8 @@
 	if ( ! current_user_can( $tax->cap->edit_terms ) )
 		wp_die( -1 );
 
-	set_current_screen( 'edit-' . $taxonomy );
+	$wp_list_table = _get_list_table( 'WP_Terms_List_Table', array( 'screen' => 'edit-' . $taxonomy ) );
 
-	$wp_list_table = _get_list_table('WP_Terms_List_Table');
-
 	if ( ! isset($_POST['tax_ID']) || ! ( $id = (int) $_POST['tax_ID'] ) )
 		wp_die( -1 );
 
Index: wp-admin/includes/class-wp-users-list-table.php
===================================================================
--- wp-admin/includes/class-wp-users-list-table.php	(revision 21813)
+++ wp-admin/includes/class-wp-users-list-table.php	(working copy)
@@ -12,17 +12,17 @@
 	var $site_id;
 	var $is_site_users;
 
-	function __construct() {
-		$screen = get_current_screen();
-		$this->is_site_users = 'site-users-network' == $screen->id;
+	function __construct( $args = array() ) {
+		parent::__construct( array(
+			'singular' => 'user',
+			'plural'   => 'users',
+			'screen'   => isset( $args['screen'] ) ? $args['screen'] : null,
+		) );
 
+		$this->is_site_users = 'site-users-network' == $this->screen->id;
+
 		if ( $this->is_site_users )
 			$this->site_id = isset( $_REQUEST['id'] ) ? intval( $_REQUEST['id'] ) : 0;
-
-		parent::__construct( array(
-			'singular' => 'user',
-			'plural'   => 'users'
-		) );
 	}
 
 	function ajax_user_can() {
Index: wp-admin/includes/class-wp-list-table.php
===================================================================
--- wp-admin/includes/class-wp-list-table.php	(revision 21813)
+++ wp-admin/includes/class-wp-list-table.php	(working copy)
@@ -81,15 +81,16 @@
 		$args = wp_parse_args( $args, array(
 			'plural' => '',
 			'singular' => '',
-			'ajax' => false
+			'ajax' => false,
+			'screen' => null,
 		) );
 
-		$screen = get_current_screen();
+		$this->screen = convert_to_screen( $args['screen'] );
 
-		add_filter( "manage_{$screen->id}_columns", array( &$this, 'get_columns' ), 0 );
+		add_filter( "manage_{$this->screen->id}_columns", array( &$this, 'get_columns' ), 0 );
 
 		if ( !$args['plural'] )
-			$args['plural'] = $screen->base;
+			$args['plural'] = $this->screen->base;
 
 		$args['plural'] = sanitize_key( $args['plural'] );
 		$args['singular'] = sanitize_key( $args['singular'] );
@@ -242,10 +243,8 @@
 	 * @access public
 	 */
 	function views() {
-		$screen = get_current_screen();
-
 		$views = $this->get_views();
-		$views = apply_filters( 'views_' . $screen->id, $views );
+		$views = apply_filters( 'views_' . $this->screen->id, $views );
 
 		if ( empty( $views ) )
 			return;
@@ -278,12 +277,10 @@
 	 * @access public
 	 */
 	function bulk_actions() {
-		$screen = get_current_screen();
-
 		if ( is_null( $this->_actions ) ) {
 			$no_new_actions = $this->_actions = $this->get_bulk_actions();
 			// This filter can currently only be used to remove actions.
-			$this->_actions = apply_filters( 'bulk_actions-' . $screen->id, $this->_actions );
+			$this->_actions = apply_filters( 'bulk_actions-' . $this->screen->id, $this->_actions );
 			$this->_actions = array_intersect_assoc( $this->_actions, $no_new_actions );
 			$two = '';
 		} else {
@@ -604,13 +601,11 @@
 		if ( isset( $this->_column_headers ) )
 			return $this->_column_headers;
 
-		$screen = get_current_screen();
+		$columns = get_column_headers( $this->screen );
+		$hidden = get_hidden_columns( $this->screen );
 
-		$columns = get_column_headers( $screen );
-		$hidden = get_hidden_columns( $screen );
+		$_sortable = apply_filters( "manage_{$this->screen->id}_sortable_columns", $this->get_sortable_columns() );
 
-		$_sortable = apply_filters( "manage_{$screen->id}_sortable_columns", $this->get_sortable_columns() );
-
 		$sortable = array();
 		foreach ( $_sortable as $id => $data ) {
 			if ( empty( $data ) )
@@ -651,8 +646,6 @@
 	 * @param bool $with_id Whether to set the id attribute or not
 	 */
 	function print_column_headers( $with_id = true ) {
-		$screen = get_current_screen();
-
 		list( $columns, $hidden, $sortable ) = $this->get_column_info();
 
 		$current_url = set_url_scheme( 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'] );
@@ -914,13 +907,11 @@
 	 * @access private
 	 */
 	function _js_vars() {
-		$current_screen = get_current_screen();
-
 		$args = array(
 			'class'  => get_class( $this ),
 			'screen' => array(
-				'id'   => $current_screen->id,
-				'base' => $current_screen->base,
+				'id'   => $this->screen->id,
+				'base' => $this->screen->base,
 			)
 		);
 
Index: wp-admin/includes/class-wp-ms-themes-list-table.php
===================================================================
--- wp-admin/includes/class-wp-ms-themes-list-table.php	(revision 21813)
+++ wp-admin/includes/class-wp-ms-themes-list-table.php	(working copy)
@@ -12,24 +12,24 @@
 	var $site_id;
 	var $is_site_themes;
 
-	function __construct() {
+	function __construct( $args = array() ) {
 		global $status, $page;
 
+		parent::__construct( array(
+			'plural' => 'themes',
+			'screen' => isset( $args['screen'] ) ? $args['screen'] : null,
+		) );
+
 		$status = isset( $_REQUEST['theme_status'] ) ? $_REQUEST['theme_status'] : 'all';
 		if ( !in_array( $status, array( 'all', 'enabled', 'disabled', 'upgrade', 'search', 'broken' ) ) )
 			$status = 'all';
 
 		$page = $this->get_pagenum();
 
-		$screen = get_current_screen();
-		$this->is_site_themes = ( 'site-themes-network' == $screen->id ) ? true : false;
+		$this->is_site_themes = ( 'site-themes-network' == $this->screen->id ) ? true : false;
 
 		if ( $this->is_site_themes )
 			$this->site_id = isset( $_REQUEST['id'] ) ? intval( $_REQUEST['id'] ) : 0;
-
-		parent::__construct( array(
-			'plural' => 'themes'
-		) );
 	}
 
 	function get_table_classes() {
Index: wp-admin/includes/class-wp-plugins-list-table.php
===================================================================
--- wp-admin/includes/class-wp-plugins-list-table.php	(revision 21813)
+++ wp-admin/includes/class-wp-plugins-list-table.php	(working copy)
@@ -9,9 +9,14 @@
  */
 class WP_Plugins_List_Table extends WP_List_Table {
 
-	function __construct() {
+	function __construct( $args = array() ) {
 		global $status, $page;
 
+		parent::__construct( array(
+			'plural' => 'plugins',
+			'screen' => isset( $args['screen'] ) ? $args['screen'] : null,
+		) );
+
 		$status = 'all';
 		if ( isset( $_REQUEST['plugin_status'] ) && in_array( $_REQUEST['plugin_status'], array( 'active', 'inactive', 'recently_activated', 'upgrade', 'mustuse', 'dropins', 'search' ) ) )
 			$status = $_REQUEST['plugin_status'];
@@ -20,10 +25,6 @@
 			$_SERVER['REQUEST_URI'] = add_query_arg('s', stripslashes($_REQUEST['s']) );
 
 		$page = $this->get_pagenum();
-
-		parent::__construct( array(
-			'plural' => 'plugins',
-		) );
 	}
 
 	function get_table_classes() {
@@ -50,9 +51,7 @@
 			'dropins' => array()
 		);
 
-		$screen = get_current_screen();
-
-		if ( ! is_multisite() || ( $screen->is_network && current_user_can('manage_network_plugins') ) ) {
+		if ( ! is_multisite() || ( $this->screen->is_network && current_user_can('manage_network_plugins') ) ) {
 			if ( apply_filters( 'show_advanced_plugins', true, 'mustuse' ) )
 				$plugins['mustuse'] = get_mu_plugins();
 			if ( apply_filters( 'show_advanced_plugins', true, 'dropins' ) )
@@ -71,7 +70,7 @@
 
 		set_transient( 'plugin_slugs', array_keys( $plugins['all'] ), 86400 );
 
-		if ( ! $screen->is_network ) {
+		if ( ! $this->screen->is_network ) {
 			$recently_activated = get_option( 'recently_activated', array() );
 
 			$one_week = 7*24*60*60;
@@ -83,15 +82,15 @@
 
 		foreach ( (array) $plugins['all'] as $plugin_file => $plugin_data ) {
 			// Filter into individual sections
-			if ( is_multisite() && ! $screen->is_network && is_network_only_plugin( $plugin_file ) ) {
+			if ( is_multisite() && ! $this->screen->is_network && is_network_only_plugin( $plugin_file ) ) {
 				unset( $plugins['all'][ $plugin_file ] );
-			} elseif ( ! $screen->is_network && is_plugin_active_for_network( $plugin_file ) ) {
+			} elseif ( ! $this->screen->is_network && is_plugin_active_for_network( $plugin_file ) ) {
 				unset( $plugins['all'][ $plugin_file ] );
-			} elseif ( ( ! $screen->is_network && is_plugin_active( $plugin_file ) )
-				|| ( $screen->is_network && is_plugin_active_for_network( $plugin_file ) ) ) {
+			} elseif ( ( ! $this->screen->is_network && is_plugin_active( $plugin_file ) )
+				|| ( $this->screen->is_network && is_plugin_active_for_network( $plugin_file ) ) ) {
 				$plugins['active'][ $plugin_file ] = $plugin_data;
 			} else {
-				if ( !$screen->is_network && isset( $recently_activated[ $plugin_file ] ) ) // Was the plugin recently activated?
+				if ( ! $this->screen->is_network && isset( $recently_activated[ $plugin_file ] ) ) // Was the plugin recently activated?
 					$plugins['recently_activated'][ $plugin_file ] = $plugin_data;
 				$plugins['inactive'][ $plugin_file ] = $plugin_data;
 			}
@@ -124,7 +123,7 @@
 			uasort( $this->items, array( &$this, '_order_callback' ) );
 		}
 
-		$plugins_per_page = $this->get_items_per_page( str_replace( '-', '_', $screen->id . '_per_page' ), 999 );
+		$plugins_per_page = $this->get_items_per_page( str_replace( '-', '_', $this->screen->id . '_per_page' ), 999 );
 
 		$start = ( $page - 1 ) * $plugins_per_page;
 
@@ -236,15 +235,13 @@
 
 		$actions = array();
 
-		$screen = get_current_screen();
-
 		if ( 'active' != $status )
-			$actions['activate-selected'] = $screen->is_network ? __( 'Network Activate' ) : __( 'Activate' );
+			$actions['activate-selected'] = $this->screen->is_network ? __( 'Network Activate' ) : __( 'Activate' );
 
 		if ( 'inactive' != $status && 'recent' != $status )
-			$actions['deactivate-selected'] = $screen->is_network ? __( 'Network Deactivate' ) : __( 'Deactivate' );
+			$actions['deactivate-selected'] = $this->screen->is_network ? __( 'Network Deactivate' ) : __( 'Deactivate' );
 
-		if ( !is_multisite() || $screen->is_network ) {
+		if ( !is_multisite() || $this->screen->is_network ) {
 			if ( current_user_can( 'update_plugins' ) )
 				$actions['update-selected'] = __( 'Update' );
 			if ( current_user_can( 'delete_plugins' ) && ( 'active' != $status ) )
@@ -271,9 +268,7 @@
 
 		echo '<div class="alignleft actions">';
 
-		$screen = get_current_screen();
-
-		if ( ! $screen->is_network && 'recently_activated' == $status )
+		if ( ! $this->screen->is_network && 'recently_activated' == $status )
 			submit_button( __( 'Clear List' ), 'small', 'clear-recent-list', false );
 		elseif ( 'top' == $which && 'mustuse' == $status )
 			echo '<p>' . sprintf( __( 'Files in the <code>%s</code> directory are executed automatically.' ), str_replace( ABSPATH, '/', WPMU_PLUGIN_DIR ) ) . '</p>';
@@ -293,9 +288,7 @@
 	function display_rows() {
 		global $status;
 
-		$screen = get_current_screen();
-
-		if ( is_multisite() && !$screen->is_network && in_array( $status, array( 'mustuse', 'dropins' ) ) )
+		if ( is_multisite() && ! $this->screen->is_network && in_array( $status, array( 'mustuse', 'dropins' ) ) )
 			return;
 
 		foreach ( $this->items as $plugin_file => $plugin_data )
@@ -307,8 +300,6 @@
 
 		$context = $status;
 
-		$screen = get_current_screen();
-
 		// preorder
 		$actions = array(
 			'deactivate' => '',
@@ -337,12 +328,12 @@
 			if ( $plugin_data['Description'] )
 				$description .= '<p>' . $plugin_data['Description'] . '</p>';
 		} else {
-			if ( $screen->is_network )
+			if ( $this->screen->is_network )
 				$is_active = is_plugin_active_for_network( $plugin_file );
 			else
 				$is_active = is_plugin_active( $plugin_file );
 
-			if ( $screen->is_network ) {
+			if ( $this->screen->is_network ) {
 				if ( $is_active ) {
 					if ( current_user_can( 'manage_network_plugins' ) )
 						$actions['deactivate'] = '<a href="' . wp_nonce_url('plugins.php?action=deactivate&amp;plugin=' . $plugin_file . '&amp;plugin_status=' . $context . '&amp;paged=' . $page . '&amp;s=' . $s, 'deactivate-plugin_' . $plugin_file) . '" title="' . esc_attr__('Deactivate this plugin') . '">' . __('Network Deactivate') . '</a>';
@@ -361,13 +352,13 @@
 					if ( ! is_multisite() && current_user_can('delete_plugins') )
 						$actions['delete'] = '<a href="' . wp_nonce_url('plugins.php?action=delete-selected&amp;checked[]=' . $plugin_file . '&amp;plugin_status=' . $context . '&amp;paged=' . $page . '&amp;s=' . $s, 'bulk-plugins') . '" title="' . esc_attr__('Delete this plugin') . '" class="delete">' . __('Delete') . '</a>';
 				} // end if $is_active
-			 } // end if $screen->is_network
+			 } // end if $this->screen->is_network
 
-			if ( ( ! is_multisite() || $screen->is_network ) && current_user_can('edit_plugins') && is_writable(WP_PLUGIN_DIR . '/' . $plugin_file) )
+			if ( ( ! is_multisite() || $this->screen->is_network ) && current_user_can('edit_plugins') && is_writable(WP_PLUGIN_DIR . '/' . $plugin_file) )
 				$actions['edit'] = '<a href="plugin-editor.php?file=' . $plugin_file . '" title="' . esc_attr__('Open this file in the Plugin Editor') . '" class="edit">' . __('Edit') . '</a>';
 		} // end if $context
 
-		$prefix = $screen->is_network ? 'network_admin_' : '';
+		$prefix = $this->screen->is_network ? 'network_admin_' : '';
 		$actions = apply_filters( $prefix . 'plugin_action_links', array_filter( $actions ), $plugin_file, $plugin_data, $context );
 		$actions = apply_filters( $prefix . "plugin_action_links_$plugin_file", $actions, $plugin_file, $plugin_data, $context );
 
Index: wp-admin/includes/class-wp-themes-list-table.php
===================================================================
--- wp-admin/includes/class-wp-themes-list-table.php	(revision 21813)
+++ wp-admin/includes/class-wp-themes-list-table.php	(working copy)
@@ -12,9 +12,10 @@
 	protected $search_terms = array();
 	var $features = array();
 
-	function __construct() {
+	function __construct( $args = array() ) {
 		parent::__construct( array(
 			'ajax' => true,
+			'screen' => isset( $args['screen'] ) ? $args['screen'] : null,
 		) );
 	}