Block Editor: Do not load a default font family for themes with theme.json.

This matches the behavior that has been in place in the gutenberg plugin.
The idea is that this makes the editor match the frontend by default for these themes.
If they use a custom font, they'll have to provide it for the editor as editor styles.

Props nosolosw.

Built from https://develop.svn.wordpress.org/trunk@51240


git-svn-id: http://core.svn.wordpress.org/trunk@50849 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/block-editor.php

@@ -470,12 +470,17 @@ function block_editor_rest_api_preload( array $preload_paths, $block_editor_cont
 function get_block_editor_theme_styles() {
 	global $editor_styles;
 
-	$styles = array(
-		array(
-			'css'            => 'body { font-family: -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Oxygen-Sans,Ubuntu,Cantarell,"Helvetica Neue",sans-serif }',
-			'__unstableType' => 'core',
-		),
-	);
+	if ( ! WP_Theme_JSON_Resolver::theme_has_support() ) {
+		$styles = array(
+			array(
+				'css'            => 'body { font-family: -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Oxygen-Sans,Ubuntu,Cantarell,"Helvetica Neue",sans-serif }',
+				'__unstableType' => 'core',
+			),
+		);
+	} else {
+		$styles = array();
+	}
+
 	if ( $editor_styles && current_theme_supports( 'editor-styles' ) ) {
 		foreach ( $editor_styles as $style ) {
 			if ( preg_match( '~^(https?:)?//~', $style ) ) {

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.8-beta3-51239';
+$wp_version = '5.8-beta3-51240';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.