Make source information on conditions mandatory in CPS

tests/compiler/dart2js/sourcemaps/source_mapping_invokes_test.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'source_mapping_tester.dart';
-import 'sourcemap_helper.dart';
-import 'package:compiler/src/io/position_information.dart';
 
 void main() {
-  test(['invokes'], whiteListFunction: (String config, String file) {
-    if (config == 'cps') {
-      return (CodePoint codePoint) {
-        // Temporarily allow missing code points on expression statements.
-        return codePoint.kind == StepKind.EXPRESSION_STATEMENT;
-      };
-    }
-    return emptyWhiteList;
-  });
+  test(['invokes']);
 }