Don't save highlithing errors to cache

Summary:
If I have Pygments enabled in config but `pygmentize` doesn't work then unhighlighted source is stored to cache.
If I later make `pygmentize` work then the unhighlighted source is still loaded from the cache.

Test Plan:
Break `pygmentize`.
View a diff with JS files.
Fix `pygmenize`.
View the diff again.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, gatos99, Koolvin

Differential Revision: https://secure.phabricator.com/D2227

src/applications/markup/syntax/PhabricatorSyntaxHighlighter.php

@@ -1,7 +1,7 @@
 <?php
 
 /*
- * Copyright 2011 Facebook, Inc.
+ * Copyright 2012 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -39,12 +39,12 @@ final class PhabricatorSyntaxHighlighter {
   public static function highlightWithFilename($filename, $source) {
     $engine = self::newEngine();
     $language = $engine->getLanguageFromFilename($filename);
-    return $engine->getHighlightFuture($language, $source)->resolve();
+    return $engine->highlightSource($language, $source);
   }
 
   public static function highlightWithLanguage($language, $source) {
     $engine = self::newEngine();
-    return $engine->getHighlightFuture($language, $source)->resolve();
+    return $engine->highlightSource($language, $source);
   }