Revisions: Set PHP time limit when generating revision diffs vis Ajax.

This aims to avoid hanging PHP processes if a plugin inadvertently attempts to request a large number of revision diffs.

Follow-up to [24520], [24707], [59039].

Props madpeter, lovesoni1999, debarghyabanerjee, pbearne, desrosj, SergeyBiryukov.
Fixes #49291.

git-svn-id: https://develop.svn.wordpress.org/trunk@59288 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/ajax-actions.php

@@ -3556,9 +3556,9 @@ function wp_ajax_get_revision_diffs() {
 
 	$return = array();
 
-	// Removes the script timeout limit by setting it to 0 allowing ample time for diff UI setup.
 	if ( function_exists( 'set_time_limit' ) ) {
-		set_time_limit( 0 );
+		// Increase the script timeout limit to allow ample time for diff UI setup.
+		set_time_limit( 5 * MINUTE_IN_SECONDS );
 	}
 
 	foreach ( $_REQUEST['compare'] as $compare_key ) {