Make DownloadScheme.isAuthSupported an abstract method

It is too easy to forget to override isAuthSupported in download
schemes that support but do not require authentication.  Make it
abstract so anyone adding a new download scheme has to make an
explicit choice about whether it should show up on changes that are
not world-readable.

Change-Id: Ifbc70c0d3b6eea08ceee726317381cabd3892e03
diff --git a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/config/DownloadScheme.java b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/config/DownloadScheme.java
index 20eda97..d81657a 100644
--- a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/config/DownloadScheme.java
+++ b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/config/DownloadScheme.java
@@ -30,9 +30,7 @@
   public abstract boolean isAuthRequired();
 
   /** @return whether this scheme supports authentication */
-  public boolean isAuthSupported() {
-    return isAuthRequired();
-  }
+  public abstract boolean isAuthSupported();
 
   /** @return whether the download scheme is enabled */
   public abstract boolean isEnabled();
diff --git a/plugins/download-commands b/plugins/download-commands
index fbec6d1..fe2bc6b 160000
--- a/plugins/download-commands
+++ b/plugins/download-commands
@@ -1 +1 @@
-Subproject commit fbec6d1a66daf838a6a795e7ebd470780a398d6f
+Subproject commit fe2bc6be5ef964a5df247a85f82c0155dc2f8876