MDL-14898 upgraded html purifier to 3.1.0 in HEAD

lib/htmlpurifier/HTMLPurifier/Strategy.php

@@ -8,13 +8,8 @@
  * features, such as custom tags, custom parsing of text, etc.
  */
 
-HTMLPurifier_ConfigSchema::define(
-    'Core', 'EscapeInvalidTags', false, 'bool',
-    'When true, invalid tags will be written back to the document as plain '.
-    'text.  Otherwise, they are silently dropped.'
-);
  
-class HTMLPurifier_Strategy
+abstract class HTMLPurifier_Strategy
 {
     
     /**
@@ -24,9 +19,7 @@ class HTMLPurifier_Strategy
      * @param $config Configuration options
      * @returns Processed array of token objects.
      */
-    function execute($tokens, $config, &$context) {
-        trigger_error('Cannot call abstract function', E_USER_ERROR);
-    }
+    abstract public function execute($tokens, $config, $context);
     
 }