PostReview: Spare constructing ChangeData by using ChangeNotes

Change-Id: Iea34ee9514f191930ca0f6829213bbfb0304dace
diff --git a/java/com/google/gerrit/server/restapi/change/PostReview.java b/java/com/google/gerrit/server/restapi/change/PostReview.java
index 562bdf8..73b38b2 100644
--- a/java/com/google/gerrit/server/restapi/change/PostReview.java
+++ b/java/com/google/gerrit/server/restapi/change/PostReview.java
@@ -1228,9 +1228,10 @@
     }
 
     private boolean isReviewer(ChangeContext ctx) {
-      ChangeData cd = changeDataFactory.create(ctx.getNotes());
-      ReviewerSet reviewers = cd.reviewers();
-      return reviewers.byState(REVIEWER).contains(ctx.getAccountId());
+      return approvalsUtil
+          .getReviewers(ctx.getNotes())
+          .byState(REVIEWER)
+          .contains(ctx.getAccountId());
     }
 
     private boolean updateLabels(ProjectState projectState, ChangeContext ctx)