Add mixin interface for matchable predicates

Only change predicates need to have a match method, because for
historic reasons changes may be loaded from multiple sources.
Predicates for other indices do not need to implement a match method
because the data is always loaded from the index. An exception are
the predicates that check visibility for which a match method is
always required.

Change-Id: I3492bc83b6faf6708ab0102a49463aa0d4a3d10b
Signed-off-by: Edwin Kempin <ekempin@google.com>

gerrit-server/src/test/java/com/google/gerrit/server/index/change/FakeQueryBuilder.java

@@ -18,7 +18,6 @@ import com.google.gerrit.server.query.OperatorPredicate;
 import com.google.gerrit.server.query.Predicate;
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.gerrit.server.query.change.ChangeQueryBuilder;
-import com.google.gwtorm.server.OrmException;
 
 import org.junit.Ignore;
 
@@ -44,16 +43,6 @@ public class FakeQueryBuilder extends ChangeQueryBuilder {
   }
 
   private Predicate<ChangeData> predicate(String name, String value) {
-    return new OperatorPredicate<ChangeData>(name, value) {
-      @Override
-      public boolean match(ChangeData object) throws OrmException {
-        return false;
-      }
-
-      @Override
-      public int getCost() {
-        return 0;
-      }
-    };
+    return new OperatorPredicate<ChangeData>(name, value) {};
   }
 }

gerrit-server/src/test/java/com/google/gerrit/server/query/PredicateTest.java

@@ -24,16 +24,6 @@ public abstract class PredicateTest extends GerritBaseTests {
     protected TestPredicate(String name, String value) {
       super(name, value);
     }
-
-    @Override
-    public boolean match(String object) {
-      return false;
-    }
-
-    @Override
-    public int getCost() {
-      return 0;
-    }
   }
 
   protected static TestPredicate f(String name, String value) {