Viewerize ArcBundle file loading callbacks

Summary: Ref T603. Clean these up and move them to a single place.

Test Plan:
  - Downloaded a raw diff.
  - Enabled "attach diffs", created a revision, got an email with a diff.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D7179

src/applications/files/query/PhabricatorFileBundleLoader.php

@@ -0,0 +1,27 @@
+<?php
+
+/**
+ * Callback provider for loading @{class@arcanist:ArcanistBundle} file data
+ * stored in the Files application.
+ */
+final class PhabricatorFileBundleLoader {
+
+  private $viewer;
+
+  public function setViewer(PhabricatorUser $viewer) {
+    $this->viewer = $viewer;
+    return $this;
+  }
+
+  public function loadFileData($phid) {
+    $file = id(new PhabricatorFileQuery())
+      ->setViewer($this->viewer)
+      ->withPHIDs(array($phid))
+      ->executeOne();
+    if (!$file) {
+      return null;
+    }
+    return $file->loadFileData();
+  }
+
+}