Return fulltext tokens from the Ferret fulltext engine

Summary:
Ref T12819. These render the little "Searched For: X, Y, U V" hint about how something was parsed.

(This might get a "substring" color or "title only" color or something in the future.)

Test Plan: {F5178807}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12819

Differential Revision: https://secure.phabricator.com/D18589

src/applications/search/fulltextstorage/PhabricatorFerretFulltextStorageEngine.php

@@ -86,6 +86,10 @@ final class PhabricatorFerretFulltextStorageEngine
       $type_results[$type] = $results;
 
       $metadata += $engine_query->getFerretMetadata();
+
+      if (!$this->fulltextTokens) {
+        $this->fulltextTokens = $engine_query->getFerretTokens();
+      }
     }
 
     $list = array();

src/infrastructure/query/policy/PhabricatorCursorPagedPolicyAwareQuery.php

@@ -1469,6 +1469,17 @@ abstract class PhabricatorCursorPagedPolicyAwareQuery
     return $this;
   }
 
+  public function getFerretTokens() {
+    if (!$this->supportsFerretEngine()) {
+      throw new Exception(
+        pht(
+          'Query ("%s") does not support the Ferret fulltext engine.',
+          get_class($this)));
+    }
+
+    return $this->ferretTokens;
+  }
+
   public function withFerretConstraint(
     PhabricatorFerretEngine $engine,
     array $fulltext_tokens) {