Theme_Upgrader::bulk_upgrade

			array(
				'package'           => $r['package'],
				'destination'       => get_theme_root( $theme ),
				'clear_destination' => true,
				'clear_working'     => true,
				'hook_extra'        => array(
					'theme'  => $theme,
					'type'   => 'theme',
					'action' => 'update',
				),
			)
		);

		remove_action( 'upgrader_process_complete', 'wp_clean_themes_cache', 9 );
		remove_filter( 'upgrader_pre_install', array( $this, 'current_before' ) );
		remove_filter( 'upgrader_post_install', array( $this, 'current_after' ) );
		remove_filter( 'upgrader_clear_destination', array( $this, 'delete_old_theme' ) );

		if ( ! $this->result || is_wp_error( $this->result ) ) {
			return $this->result;
		}

		wp_clean_themes_cache( $parsed_args['clear_update_cache'] );

		// Ensure any future auto-update failures trigger a failure email by removing
		// the last failure notification from the list when themes update successfully.
		$past_failure_emails = get_option( 'auto_plugin_theme_update_emails', array() );

		if ( isset( $past_failure_emails[ $theme ] ) ) {
			unset( $past_failure_emails[ $theme ] );
			update_option( 'auto_plugin_theme_update_emails', $past_failure_emails );
		}

		return true;
	}

	/**
	 * Upgrade several themes at once.
	 *
	 * @since 3.0.0
	 * @since 3.7.0 The `$args` parameter was added, making clearing the update cache optional.
	 *
	 * @param string[] $themes Array of the theme slugs.
	 * @param array    $args {
	 *     Optional. Other arguments for upgrading several themes at once. Default empty array.
	 *
	 *     @type bool $clear_update_cache Whether to clear the update cache if successful.
	 *                                    Default true.
	 * }
	 * @return array[]|false An array of results, or false if unable to connect to the filesystem.
	 */
	public function bulk_upgrade( $themes, $args = array() ) {
		$defaults    = array(
			'clear_update_cache' => true,
		);
		$parsed_args = wp_parse_args( $args, $defaults );

		$this->init();
		$this->bulk = true;
		$this->upgrade_strings();

		$current = get_site_transient( 'update_themes' );

		add_filter( 'upgrader_pre_install', array( $this, 'current_before' ), 10, 2 );
		add_filter( 'upgrader_post_install', array( $this, 'current_after' ), 10, 2 );
		add_filter( 'upgrader_clear_destination', array( $this, 'delete_old_theme' ), 10, 4 );

		$this->skin->header();

		// Connect to the filesystem first.
		$res = $this->fs_connect( array( WP_CONTENT_DIR ) );
		if ( ! $res ) {
			$this->skin->footer();
			return false;
		}

		$this->skin->bulk_header();

		/*
		 * Only start maintenance mode if:
		 * - running Multisite and there are one or more themes specified, OR
		 * - a theme with an update available is currently in use.
		 * @todo For multisite, maintenance mode should only kick in for individual sites if at all possible.
		 */
		$maintenance = ( is_multisite() && ! empty( $themes ) );
		foreach ( $themes as $theme ) {
			$maintenance = $maintenance || get_stylesheet() === $theme || get_template() === $theme;
		}
		if ( $maintenance ) {
			$this->maintenance_mode( true );
		}

		$results = array();

		$this->update_count   = count( $themes );
		$this->update_current = 0;
		foreach ( $themes as $theme ) {
			$this->update_current++;

			$this->skin->theme_info = $this->theme_info( $theme );

			if ( ! isset( $current->response[ $theme ] ) ) {
				$this->skin->set_result( true );
				$this->skin->before();
				$this->skin->feedback( 'up_to_date' );
				$this->skin->after();
				$results[ $theme ] = true;
				continue;
			}

			// Get the URL to the zip file.
			$r = $current->response[ $theme ];