Use insert_marker over set_marker

Use the method implemented in WordPress#6982
to avoid duplicating the same functionality.

src/wp-includes/html-api/class-wp-html-active-formatting-elements.php

@@ -86,6 +86,22 @@ public function current_node() {
 		return $current_node ? $current_node : null;
 	}
 
+	/**
+	 * Inserts a "marker" at the end of the list of active formatting elements.
+	 *
+	 * > The markers are inserted when entering applet, object, marquee,
+	 * > template, td, th, and caption elements, and are used to prevent
+	 * > formatting from "leaking" into applet, object, marquee, template,
+	 * > td, th, and caption elements.
+	 *
+	 * @see https://html.spec.whatwg.org/#concept-parser-marker
+	 *
+	 * @since 6.7.0
+	 */
+	public function insert_marker() {
+		$this->push( new WP_HTML_Token( null, 'marker', false ) );
+	}
+
 	/**
 	 * Pushes a node onto the stack of active formatting elements.
 	 *
@@ -185,10 +201,6 @@ public function walk_up() {
 		}
 	}
 
-	public function set_marker() {
-		$this->push( new WP_HTML_Token( null, 'marker', false ) );
-	}
-
 	/**
 	 * Clears the list of active formatting elements up to the last marker.
 	 *
@@ -208,9 +220,8 @@ public function set_marker() {
 	 */
 	public function clear_up_to_last_marker(): void {
 		foreach ( $this->walk_up() as $item ) {
-			$is_marker = 'marker' === $item->node_name;
 			array_pop( $this->stack );
-			if ( $is_marker ) {
+			if ( 'marker' === $item->node_name ) {
 				break;
 			}
 		}

src/wp-includes/html-api/class-wp-html-processor.php

@@ -1776,7 +1776,7 @@ private function step_in_table() {
 			 */
 			case '+CAPTION':
 				$this->clear_stack_to_table_context();
-				$this->state->active_formatting_elements->set_marker();
+				$this->state->active_formatting_elements->insert_marker();
 				$this->insert_html_element( $this->state->current_token );
 				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_CAPTION;
 				return true;
@@ -2113,7 +2113,7 @@ private function step_in_row() {
 			case '+TD':
 				$this->clear_stack_to_table_row_context();
 				$this->insert_html_element( $this->state->current_token );
-				$this->state->active_formatting_elements->set_marker();
+				$this->state->active_formatting_elements->insert_marker();
 				return true;
 
 			/*