Media: Ensure custom header image tag supports loading optimization attributes.

This changeset is a follow up to [56037] and ensures that the `get_header_image_tag()` function receives the benefits of `wp_get_loading_optimization_attributes()` as well. Prior to `fetchpriority` support, this was not needed since the header image should never be lazy-loaded, but the image certainly is a `fetchpriority` candidate, so therefore it is crucial to have it supported.

Props felipeelia, spacedmonkey, mukesh27, westonruter, flixos90.
Fixes #58680.

Built from https://develop.svn.wordpress.org/trunk@56142


git-svn-id: http://core.svn.wordpress.org/trunk@55654 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/media.php

@@ -5643,6 +5643,11 @@ function wp_get_loading_optimization_attributes( $tag_name, $attr, $context ) {
 		return $postprocess( $loading_attrs, true );
 	}
 
+	// The custom header image is always expected to be in the header.
+	if ( 'get_header_image_tag' === $context ) {
+		return $postprocess( $loading_attrs, true );
+	}
+
 	// Special handling for programmatically created image tags.
 	if ( 'the_post_thumbnail' === $context || 'wp_get_attachment_image' === $context ) {
 		/*

wp-includes/theme.php

@@ -1241,6 +1241,7 @@ function get_header_image_tag( $attr = array() ) {
 			'width'    => $width,
 			'height'   => $height,
 			'alt'      => $alt,
+			'decoding' => 'async',
 		)
 	);
 
@@ -1265,6 +1266,29 @@ function get_header_image_tag( $attr = array() ) {
 		}
 	}
 
+	$attr = array_merge(
+		$attr,
+		wp_get_loading_optimization_attributes( 'img', $attr, 'get_header_image_tag' )
+	);
+
+	/*
+	 * If the default value of `lazy` for the `loading` attribute is overridden
+	 * to omit the attribute for this image, ensure it is not included.
+	 */
+	if ( isset( $attr['loading'] ) && ! $attr['loading'] ) {
+		unset( $attr['loading'] );
+	}
+
+	// If the `fetchpriority` attribute is overridden and set to false or an empty string.
+	if ( isset( $attr['fetchpriority'] ) && ! $attr['fetchpriority'] ) {
+		unset( $attr['fetchpriority'] );
+	}
+
+	// If the `decoding` attribute is overridden and set to false or an empty string.
+	if ( isset( $attr['decoding'] ) && ! $attr['decoding'] ) {
+		unset( $attr['decoding'] );
+	}
+
 	/**
 	 * Filters the list of header image attributes.
 	 *

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.3-beta3-56141';
+$wp_version = '6.3-beta3-56142';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.