Add a shrinking reduction for dead continuation parameters.

pkg/analyzer2dart/test/end2end_data.dart

 // Copyright (c) 2014, 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.
 
 /// Test data for the end2end test.
 library test.end2end.data;
 
 import 'test_helper.dart';
 
 class TestSpec extends TestSpecBase {
@@ skipping 742 matching lines @@
 
     const TestSpec('''
 main(a) {
   var i;
   for (i in a) {
     print(i);
   }
 }
 ''', '''
 main(a) {
-  var i, v0 = a.iterator;
+  var v0 = a.iterator;
   while (v0.moveNext()) {
     print(v0.current);
   }
 }
 '''),
   ]),
 
   const Group('Local functions', const <TestSpec>[
     const TestSpec('''
 main(a) {
@@ skipping 37 matching lines @@
 main(a) {
   return (a ? () {
     return 0;
   } : () {
     return 1;
   })();
 }
 '''),
   ]),
 ];