Give HarbormasterBuildUnitMessage a real Query class

Summary: Ref T13088. Prepares for putting test names in a separate table to release the 255-character limit.

Test Plan: Viewed revisions, buildables, builds, test lists, specific tests.

Reviewers: amckinley

Reviewed By: amckinley

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13088

Differential Revision: https://secure.phabricator.com/D20179

src/applications/differential/controller/DifferentialChangesetViewController.php

@@ -420,15 +420,17 @@ final class DifferentialChangesetViewController extends DifferentialController {
   }
 
   private function loadCoverage(DifferentialChangeset $changeset) {
+    $viewer = $this->getViewer();
+
     $target_phids = $changeset->getDiff()->getBuildTargetPHIDs();
     if (!$target_phids) {
       return null;
     }
 
-    $unit = id(new HarbormasterBuildUnitMessage())->loadAllWhere(
-      'buildTargetPHID IN (%Ls)',
-      $target_phids);
-
+    $unit = id(new HarbormasterBuildUnitMessageQuery())
+      ->setViewer($viewer)
+      ->withBuildTargetPHIDs($target_phids)
+      ->execute();
     if (!$unit) {
       return null;
     }