Document ReviewDb.nextChangeMessageId

Signed-off-by: Shawn O. Pearce <sop@google.com>
diff --git a/src/main/java/com/google/gerrit/client/reviewdb/ReviewDb.java b/src/main/java/com/google/gerrit/client/reviewdb/ReviewDb.java
index 69f1377..ef33325 100644
--- a/src/main/java/com/google/gerrit/client/reviewdb/ReviewDb.java
+++ b/src/main/java/com/google/gerrit/client/reviewdb/ReviewDb.java
@@ -122,6 +122,11 @@
   @Sequence
   int nextChangeId() throws OrmException;
 
+  /**
+   * Next id for a block of {@link ChangeMessage} records.
+   * 
+   * @see com.google.gerrit.server.ChangeUtil#messageUUID(ReviewDb)
+   */
   @Sequence
   int nextChangeMessageId() throws OrmException;
 }