title-gutenberg-external.diff

diff --git a/lib/client-assets.php b/lib/client-assets.php
index b0f3905cc..b0937a910 100644
--- a/lib/client-assets.php
+++ b/lib/client-assets.php
@@ -1131,6 +1131,41 @@ function gutenberg_default_post_format_template( $settings, $post ) {
 }
 add_filter( 'block_editor_settings', 'gutenberg_default_post_format_template', 10, 2 );
 
+/**
+ * Assigns initial edit values for the demo post content and title.
+ *
+ * @param array   $initial_edits Default initial edits.
+ * @param WP_Post $post          Post being edited.
+ *
+ * @return array Filtered initial edits, including demo content and title if
+ *               viewing the demo page.
+ */
+function gutenberg_demo_initial_edits( $initial_edits, $post ) {
+	$is_new_post = 'auto-draft' === $post->post_status;
+	$is_demo     = isset( $_GET['gutenberg-demo'] );
+	if ( $is_demo ) {
+		// Prepopulate with some test content in demo.
+		ob_start();
+		include gutenberg_dir_path() . 'post-content.php';
+		$demo_content = ob_get_clean();
+
+		$initial_edits = array_merge(
+			$initial_edits,
+			array(
+				'title'   => array(
+					'raw' => __( 'Welcome to the Gutenberg Editor', 'gutenberg' ),
+				),
+				'content' => array(
+					'raw' => $demo_content,
+				),
+			)
+		);
+	}
+
+	return $initial_edits;
+}
+add_filter( 'block_editor_initial_edits', 'gutenberg_demo_initial_edits', 10, 2 );
+
 /**
  * The code editor settings that were last captured by
  * gutenberg_capture_code_editor_settings().
@@ -1318,21 +1353,7 @@ function gutenberg_editor_scripts_and_styles( $hook ) {
 
 	// Assign initial edits, if applicable. These are not initially assigned
 	// to the persisted post, but should be included in its save payload.
-	if ( $is_new_post && $is_demo ) {
-		// Prepopulate with some test content in demo.
-		ob_start();
-		include gutenberg_dir_path() . 'post-content.php';
-		$demo_content = ob_get_clean();
-
-		$initial_edits = array(
-			'title'   => array(
-				'raw' => __( 'Welcome to the Gutenberg Editor', 'gutenberg' ),
-			),
-			'content' => array(
-				'raw' => $demo_content,
-			),
-		);
-	} elseif ( $is_new_post ) {
+	if ( $is_new_post ) {
 		// Override "(Auto Draft)" new post default title with empty string,
 		// or filtered value.
 		$initial_edits = array(
@@ -1497,6 +1518,18 @@ JS;
 	 */
 	$editor_settings = apply_filters( 'block_editor_settings', $editor_settings, $post );
 
+	/**
+	 * Filters the initial edits to pass to the block editor. An initial edit
+	 * is one which is considered non-dirtying, but should be included in the
+	 * first save payload.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param array   $initial_edits Default initial edits.
+	 * @param WP_Post $post          Post being edited.
+	 */
+	$initial_edits = apply_filters( 'block_editor_initial_edits', $initial_edits, $post );
+
 	$script = sprintf(
 		$init_script,
 		$post->post_type,