This commit: (#52819)

- removes tests that have been ported to Core already as part of WP 6.3
- Adds tests for #52370
- Changes a private method to protected so it can be used in inherited classes

lib/compat/wordpress-6.4/class-gutenberg-rest-global-styles-controller-6-4.php

@@ -266,4 +266,26 @@ protected function prepare_item_for_database( $request ) {
 		return $changes;
 	}
 
+	/**
+	 * Validate style.css as valid CSS.
+	 *
+	 * Currently just checks for invalid markup.
+	 *
+	 * @since 6.2.0
+	 * @since 6.4.0 Changed method visibility to protected.
+	 *
+	 * @param string $css CSS to validate.
+	 * @return true|WP_Error True if the input was validated, otherwise WP_Error.
+	 */
+	protected function validate_custom_css( $css ) {
+		if ( preg_match( '#</?\w+#', $css ) ) {
+			return new WP_Error(
+				'rest_custom_css_illegal_markup',
+				__( 'Markup is not allowed in CSS.', 'gutenberg' ),
+				array( 'status' => 400 )
+			);
+		}
+		return true;
+	}
+
 }

lib/compat/wordpress-6.4/class-gutenberg-rest-global-styles-revisions-controller-6-4.php

@@ -19,6 +19,7 @@ class Gutenberg_REST_Global_Styles_Revisions_Controller_6_4 extends Gutenberg_RE
 	 * Prepares the revision for the REST response.
 	 *
 	 * @since 6.3.0
+	 * @since 6.4.0 Added `behaviors` field to the response.
 	 *
 	 * @param WP_Post         $post    Post revision object.
 	 * @param WP_REST_Request $request Request object.
@@ -87,6 +88,7 @@ public function prepare_item_for_response( $post, $request ) {
 	 * Retrieves the revision's schema, conforming to JSON Schema.
 	 *
 	 * @since 6.3.0
+	 * @since 6.4.0 Added `behaviors` field to the schema properties.
 	 *
 	 * @return array Item schema data.
 	 */