public function handle_render_partials_request() {
		if ( ! $this->is_render_partials_request() ) {
			return;
		}

		/*
		 * Note that is_customize_preview() returning true will entail that the
		 * user passed the 'customize' capability check and the nonce check, since
		 * WP_Customize_Manager::setup_theme() is where the previewing flag is set.
		 */
		if ( ! is_customize_preview() ) {
			wp_send_json_error( 'expected_customize_preview', 403 );
		} elseif ( ! isset( $_POST['partials'] ) ) {
			wp_send_json_error( 'missing_partials', 400 );
		}

		// Ensure that doing selective refresh on 404 template doesn't result in fallback rendering behavior (full refreshes).
		status_header( 200 );

		$partials = json_decode( wp_unslash( $_POST['partials'] ), true );

		if ( ! is_array( $partials ) ) {
			wp_send_json_error( 'malformed_partials' );
		}

		$this->add_dynamic_partials( array_keys( $partials ) );

		/**
		 * Fires immediately before partials are rendered.
		 *
		 * Plugins may do things like call wp_enqueue_scripts() and gather a list of the scripts
		 * and styles which may get enqueued in the response.
		 *
		 * @since 4.5.0
		 *
		 * @param WP_Customize_Selective_Refresh $this     Selective refresh component.
		 * @param array                          $partials Placements' context data for the partials rendered in the request.
		 *                                                 The array is keyed by partial ID, with each item being an array of
		 *                                                 the placements' context data.
		 */
		do_action( 'customize_render_partials_before', $this, $partials );

		set_error_handler( array( $this, 'handle_error' ), error_reporting() );

		$contents = array();

		foreach ( $partials as $partial_id => $container_contexts ) {
			$this->current_partial_id = $partial_id;

			if ( ! is_array( $container_contexts ) ) {
				wp_send_json_error( 'malformed_container_contexts' );
			}

			$partial = $this->get_partial( $partial_id );

			if ( ! $partial || ! $partial->check_capabilities() ) {
				$contents[ $partial_id ] = null;
				continue;
			}

			$contents[ $partial_id ] = array();

			// @todo The array should include not only the contents, but also whether the container is included?
			if ( empty( $container_contexts ) ) {
				// Since there are no container contexts, render just once.
				$contents[ $partial_id ][] = $partial->render( null );
			} else {
				foreach ( $container_contexts as $container_context ) {
					$contents[ $partial_id ][] = $partial->render( $container_context );
				}
			}
		}
		$this->current_partial_id = null;

		restore_error_handler();

		/**
		 * Fires immediately after partials are rendered.
		 *
		 * Plugins may do things like call wp_footer() to scrape scripts output and return them
		 * via the {@see 'customize_render_partials_response'} filter.
		 *
		 * @since 4.5.0
		 *
		 * @param WP_Customize_Selective_Refresh $this     Selective refresh component.
		 * @param array                          $partials Placements' context data for the partials rendered in the request.
		 *                                                 The array is keyed by partial ID, with each item being an array of
		 *                                                 the placements' context data.
		 */
		do_action( 'customize_render_partials_after', $this, $partials );

		$response = array(
			'contents' => $contents,
		);

		if ( defined( 'WP_DEBUG_DISPLAY' ) && WP_DEBUG_DISPLAY ) {
			$response['errors'] = $this->triggered_errors;
		}

		$setting_validities             = $this->manager->validate_setting_values( $this->manager->unsanitized_post_values() );
		$exported_setting_validities    = array_map( array( $this->manager, 'prepare_setting_validity_for_js' ), $setting_validities );
		$response['setting_validities'] = $exported_setting_validities;

		/**
		 * Filters the response from rendering the partials.
		 *
		 * Plugins may use this filter to inject `$scripts` and `$styles`, which are dependencies
		 * for the partials being rendered. The response data will be available to the client via
		 * the `render-partials-response` JS event, so the client can then inject the scripts and
		 * styles into the DOM if they have not already been enqueued there.
		 *
		 * If plugins do this, they'll need to take care for any scripts that do `document.write()`
		 * and make sure that these are not injected, or else to override the function to no-op,
		 * or else the page will be destroyed.
		 *
		 * Plugins should be aware that `$scripts` and `$styles` may eventually be included by
		 * default in the response.
		 *
		 * @since 4.5.0
		 *
		 * @param array $response {
		 *     Response.
		 *
		 *     @type array $contents Associative array mapping a partial ID its corresponding array of contents
		 *                           for the containers requested.
		 *     @type array $errors   List of errors triggered during rendering of partials, if `WP_DEBUG_DISPLAY`
		 *                           is enabled.
		 * }
		 * @param WP_Customize_Selective_Refresh $this     Selective refresh component.
		 * @param array                          $partials Placements' context data for the partials rendered in the request.
		 *                                                 The array is keyed by partial ID, with each item being an array of
		 *                                                 the placements' context data.
		 */
		$response = apply_filters( 'customize_render_partials_response', $response, $this, $partials );

		wp_send_json_success( $response );
	}