Remove WP_Theme::is_child_theme() in favor of WP_Theme::parent(). see #20546.

git-svn-id: http://svn.automattic.com/wordpress/trunk@20589 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/theme-editor.php

@@ -213,7 +213,7 @@ else : ?>
 	<?php endif; ?>
 
 		<div>
-		<?php if ( is_child_theme() && ! $theme->is_child_theme() && $theme->get_template() == get_template() ) : ?>
+		<?php if ( is_child_theme() && $theme->get_stylesheet() == get_template() ) : ?>
 			<p><?php if ( is_writeable( $file ) ) { ?><strong><?php _e( 'Caution:' ); ?></strong><?php } ?>
 			<?php _e( 'This is a file in your current parent theme.' ); ?></p>
 		<?php endif; ?>

wp-includes/class-wp-theme.php

@@ -744,18 +744,6 @@ final class WP_Theme implements ArrayAccess {
 		return $this->template;
 	}
 
-	/**
-	 * Whether a theme is a child theme.
-	 *
-	 * @since 3.4.0
-	 * @access public
-	 *
-	 * @return bool True if a theme is a child theme, false otherwise.
-	 */
-	public function is_child_theme() {
-		return $this->template !== $this->stylesheet;
-	}
-
 	/**
 	 * Returns the absolute path to the directory of a theme's "stylesheet" files.
 	 *