diff -r c7c34916027a -r 177826044cd9 wp/wp-admin/js/theme.js
--- a/wp/wp-admin/js/theme.js	Mon Oct 14 18:06:33 2019 +0200
+++ b/wp/wp-admin/js/theme.js	Mon Oct 14 18:28:13 2019 +0200
@@ -1,4 +1,8 @@
-/* global _wpThemeSettings, confirm */
+/**
+ * @output wp-admin/js/theme.js
+ */
+
+/* global _wpThemeSettings, confirm, tb_position */
 window.wp = window.wp || {};
 
 ( function($) {
@@ -334,18 +338,7 @@
 			data: {
 			// Request data
 				request: _.extend({
-					per_page: 100,
-					fields: {
-						description: true,
-						tested: true,
-						requires: true,
-						rating: true,
-						downloaded: true,
-						downloadLink: true,
-						last_updated: true,
-						homepage: true,
-						num_ratings: true
-					}
+					per_page: 100
 				}, request)
 			},
 
@@ -584,16 +577,26 @@
 	// Handles .disabled classes for previous/next buttons in theme installer preview
 	setNavButtonsState: function() {
 		var $themeInstaller = $( '.theme-install-overlay' ),
-			current = _.isUndefined( this.current ) ? this.model : this.current;
+			current = _.isUndefined( this.current ) ? this.model : this.current,
+			previousThemeButton = $themeInstaller.find( '.previous-theme' ),
+			nextThemeButton = $themeInstaller.find( '.next-theme' );
 
 		// Disable previous at the zero position
 		if ( 0 === this.model.collection.indexOf( current ) ) {
-			$themeInstaller.find( '.previous-theme' ).addClass( 'disabled' );
+			previousThemeButton
+				.addClass( 'disabled' )
+				.prop( 'disabled', true );
+
+			nextThemeButton.focus();
 		}
 
 		// Disable next if the next model is undefined
 		if ( _.isUndefined( this.model.collection.at( this.model.collection.indexOf( current ) + 1 ) ) ) {
-			$themeInstaller.find( '.next-theme' ).addClass( 'disabled' );
+			nextThemeButton
+				.addClass( 'disabled' )
+				.prop( 'disabled', true );
+
+			previousThemeButton.focus();
 		}
 	},
 
@@ -2038,9 +2041,8 @@
 })( jQuery );
 
 // Align theme browser thickbox
-var tb_position;
 jQuery(document).ready( function($) {
-	tb_position = function() {
+	window.tb_position = function() {
 		var tbWindow = $('#TB_window'),
 			width = $(window).width(),
 			H = $(window).height(),