Block Editor: Load the classic layout stylesheet conditionallty.

Historically, the block editor has been opinionated about the size of the canvas and the alignments.
Themes with theme.json will have to define a "layout" in their settings and the classic stylesheet won't be loaded anymore for this.

Props nosolosw.
See #53175.

Built from https://develop.svn.wordpress.org/trunk@50992


git-svn-id: http://core.svn.wordpress.org/trunk@50601 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/script-loader.php

@@ -1510,12 +1510,13 @@ function wp_default_styles( $styles ) {
 		'wp-reset-editor-styles',
 		'wp-block-library',
 		'wp-reusable-blocks',
-
-		// This dependency shouldn't be added for themes with theme.json support
-		// It's here for backward compatibility only.
-		// A check should be added here when theme.json is backported to Core.
-		'wp-editor-classic-layout-styles',
 	);
+
+	// Only load the default layout and margin styles for themes without theme.json file.
+	if ( ! WP_Theme_JSON_Resolver::theme_has_support() ) {
+		$wp_edit_blocks_dependencies[] = 'wp-editor-classic-layout-styles';
+	}
+
 	global $editor_styles;
 	if ( ! is_array( $editor_styles ) || count( $editor_styles ) === 0 ) {
 		// Include opinionated block styles if no $editor_styles are declared, so the editor never appears broken.

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.8-alpha-50991';
+$wp_version = '5.8-alpha-50992';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.