Theme_Upgrader::check_parent_theme_filter

		if ( ! empty( $this->skin->overwrite ) ) {
			if ( 'update-theme' === $this->skin->overwrite ) {
				$this->strings['installing_package'] = __( 'Updating the theme…' );
				$this->strings['process_failed']     = __( 'Theme update failed.' );
				$this->strings['process_success']    = __( 'Theme updated successfully.' );
			}

			if ( 'downgrade-theme' === $this->skin->overwrite ) {
				$this->strings['installing_package'] = __( 'Downgrading the theme…' );
				$this->strings['process_failed']     = __( 'Theme downgrade failed.' );
				$this->strings['process_success']    = __( 'Theme downgraded successfully.' );
			}
		}
	}

	/**
	 * Check if a child theme is being installed and we need to install its parent.
	 *
	 * Hooked to the {@see 'upgrader_post_install'} filter by Theme_Upgrader::install().
	 *
	 * @since 3.4.0
	 *
	 * @param bool  $install_result
	 * @param array $hook_extra
	 * @param array $child_result
	 * @return bool
	 */
	public function check_parent_theme_filter( $install_result, $hook_extra, $child_result ) {
		// Check to see if we need to install a parent theme.
		$theme_info = $this->theme_info();

		if ( ! $theme_info->parent() ) {
			return $install_result;
		}

		$this->skin->feedback( 'parent_theme_search' );

		if ( ! $theme_info->parent()->errors() ) {
			$this->skin->feedback( 'parent_theme_currently_installed', $theme_info->parent()->display( 'Name' ), $theme_info->parent()->display( 'Version' ) );
			// We already have the theme, fall through.
			return $install_result;
		}

		// We don't have the parent theme, let's install it.
		$api = themes_api(
			'theme_information',
			array(
				'slug'   => $theme_info->get( 'Template' ),
				'fields' => array(
					'sections' => false,
					'tags'     => false,
				),
			)
		); // Save on a bit of bandwidth.

		if ( ! $api || is_wp_error( $api ) ) {
			$this->skin->feedback( 'parent_theme_not_found', $theme_info->get( 'Template' ) );
			// Don't show activate or preview actions after installation.
			add_filter( 'install_theme_complete_actions', array( $this, 'hide_activate_preview_actions' ) );
			return $install_result;
		}

		// Backup required data we're going to override:
		$child_api             = $this->skin->api;
		$child_success_message = $this->strings['process_success'];

		// Override them.
		$this->skin->api = $api;

		$this->strings['process_success_specific'] = $this->strings['parent_theme_install_success'];