Media: Prime post caches in 'wp_make_content_images_responsive()'.

In [38296] we replaced `get_post_meta()` with `wp_get_attachment_metadata()`
so that attachment metadata could be consistently filtered. However, this
results in extra post queries which were previously avoided.

This uses `_prime_post_caches()` instead of `update_meta_cache()` to improve
post caching before looping through all images to retrieve attachment metadata.

Props dlh.
Fixes #40490.

Built from https://develop.svn.wordpress.org/trunk@41315


git-svn-id: http://core.svn.wordpress.org/trunk@41146 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/media.php

@@ -1335,12 +1335,10 @@ function wp_make_content_images_responsive( $content ) {
 
 	if ( count( $attachment_ids ) > 1 ) {
 		/*
-		 * Warm object cache for use with 'get_post_meta()'.
-		 *
-		 * To avoid making a database call for each image, a single query
-		 * warms the object cache with the meta information for all images.
+		 * Warm the object cache with post and meta information for all found
+		 * images to avoid making individual database calls.
 		 */
-		update_meta_cache( 'post', array_keys( $attachment_ids ) );
+		_prime_post_caches( array_keys( $attachment_ids ), false, true );
 	}
 
 	foreach ( $selected_images as $image => $attachment_id ) {

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.9-alpha-41314';
+$wp_version = '4.9-alpha-41315';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.