ChangeControl: Disallow null as changeData for isReviewer/isVisible

There is only one caller of these methods and this caller never provides
null as input for changeData.

Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: Ia88360da953aaa4f91c692c95fc4fd8105118dbd

java/com/google/gerrit/server/permissions/ChangeControl.java

diff --git a/java/com/google/gerrit/server/permissions/ChangeControl.java b/java/com/google/gerrit/server/permissions/ChangeControl.java
index 07cb50d..782f8a1 100644
--- a/java/com/google/gerrit/server/permissions/ChangeControl.java
+++ b/java/com/google/gerrit/server/permissions/ChangeControl.java
@@ -89,7 +89,7 @@
   }
 
   /** Can this user see this change? */
-  private boolean isVisible(@Nullable ChangeData cd) {
+  private boolean isVisible(ChangeData cd) {
     if (getChange().isPrivate() && !isPrivateVisible(cd)) {
       return false;
     }
@@ -153,9 +153,8 @@
   }
 
   /** Is this user a reviewer for the change? */
-  private boolean isReviewer(@Nullable ChangeData cd) {
+  private boolean isReviewer(ChangeData cd) {
     if (getUser().isIdentifiedUser()) {
-      cd = cd != null ? cd : changeDataFactory.create(notes);
       Collection<Account.Id> results = cd.reviewers().all();
       return results.contains(getUser().getAccountId());
     }