Use the configured viewer more consistently in the Herald commit adapter

Summary: See PHI276. Ref T13048. The fix in D18933 got one callsite, but missed the one in the `callConduit()` method, so the issue isn't fully fixed in production. Convert this adapter to use a real viewer (if one is available) more thoroughly.

Test Plan: Ran rules in test console, saw field values. Will test in production again.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13048

Differential Revision: https://secure.phabricator.com/D18950

src/applications/diffusion/herald/HeraldCommitAdapter.php

@@ -135,13 +135,16 @@ final class HeraldCommitAdapter
   }
 
   public function loadAffectedPaths() {
+    $viewer = $this->getViewer();
+
     if ($this->affectedPaths === null) {
       $result = PhabricatorOwnerPathQuery::loadAffectedPaths(
         $this->getRepository(),
         $this->commit,
-        PhabricatorUser::getOmnipotentUser());
+        $viewer);
       $this->affectedPaths = $result;
     }
+
     return $this->affectedPaths;
   }
 
@@ -172,6 +175,8 @@ final class HeraldCommitAdapter
   }
 
   public function loadDifferentialRevision() {
+    $viewer = $this->getViewer();
+
     if ($this->affectedRevision === null) {
       $this->affectedRevision = false;
 
@@ -189,7 +194,7 @@ final class HeraldCommitAdapter
 
         $revision = id(new DifferentialRevisionQuery())
           ->withIDs(array($revision_id))
-          ->setViewer(PhabricatorUser::getOmnipotentUser())
+          ->setViewer($viewer)
           ->needReviewers(true)
           ->executeOne();
         if ($revision) {
@@ -197,6 +202,7 @@ final class HeraldCommitAdapter
         }
       }
     }
+
     return $this->affectedRevision;
   }
 
@@ -323,7 +329,7 @@ final class HeraldCommitAdapter
   }
 
   private function callConduit($method, array $params) {
-    $viewer = PhabricatorUser::getOmnipotentUser();
+    $viewer = $this->getViewer();
 
     $drequest = DiffusionRequest::newFromDictionary(
       array(