Refactor filter and profile in preparation for reverse sync PR

projects/packages/jetpack-mu-wpcom/src/class-jetpack-mu-wpcom.php

@@ -87,7 +87,7 @@ public static function load_features() {
 		require_once __DIR__ . '/features/site-editor-dashboard-link/site-editor-dashboard-link.php';
 		require_once __DIR__ . '/features/wpcom-site-menu/wpcom-site-menu.php';
 		require_once __DIR__ . '/features/wpcom-themes/wpcom-themes.php';
-		require_once __DIR__ . '/features/calypso-locale-sync/calypso-locale-sync.php';
+		require_once __DIR__ . '/features/calypso-locale-sync/sync-wp-admin-to-calypso.php';
 
 		// Initializers, if needed.
 		\Marketplace_Products_Updater::init();

projects/packages/jetpack-mu-wpcom/src/features/calypso-locale-sync/sync-wp-admin-to-calypso.php

@@ -0,0 +1,48 @@
+<?php
+/**
+ * Makes sure Calypso and wp-admin locales are in sync.
+ *
+ * @package automattic/jetpack-mu-wpcom
+ */
+
+use Automattic\Jetpack\Connection\Client;
+use Automattic\Jetpack\Connection\Manager as Connection_Manager;
+
+/**
+ * Sync locale updated via /wp-admin/profile.php to Calypso.
+ *
+ * @param array   $meta   Meta values and keys for the user.
+ * @param WP_User $user   User object.
+ * @param boolean $update Whether the user is being updated rather than created.
+ */
+function sync_wp_admin_locale_to_calypso( $meta, $user, $update ) {
+	$locale            = $meta['locale'];
+	$old_locale        = get_user_locale( $user );
+	$is_user_connected = ( new Connection_Manager( 'jetpack' ) )->is_user_connected();
+
+	if ( ! $update || $old_locale === $locale || ! $is_user_connected ) {
+		// Only proceed for locale changes on an existing connected WPCOM user.
+		return $meta;
+	}
+
+	if ( ! $locale ) {
+		// No locale means the "Site Default" option, which is the Site language (WPLANG).
+		$locale = get_option( 'WPLANG', '' );
+	}
+
+	Client::wpcom_json_api_request_as_user(
+		'/me/locale',
+		'2',
+		array(
+			'method' => 'POST',
+		),
+		array( 'locale' => $locale ),
+		'wpcom'
+	);
+
+	return $meta;
+}
+
+if ( function_exists( 'wpcom_is_nav_redesign_enabled' ) && wpcom_is_nav_redesign_enabled() ) {
+	add_filter( 'insert_user_meta', 'sync_wp_admin_locale_to_calypso', 8, 3 );
+}