smoke: remove unused variables and imports, added an explicit null return

test/codegen/end_to_end_test.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.
 
 /// And end-to-end test that generates code and checks that the output matches
 /// the code in `static_test.dart`. Techincally we could run the result in an
 /// isolate, but instead we decided to split that up in two tests. This test
 /// ensures that we generate the code as it was written in static_test, and
 /// separately static_test ensures that the smoke.static library behaves as
 /// expected.
@@ skipping 12 matching lines @@
 main(args) {
   final updateStaticTest = args.length > 0 && args[0] == '--update_static_test';
 
   test('static_test is up to date', () {
     var scriptPath = path.fromUri(Platform.script);
     var testDir = path.dirname(path.dirname(scriptPath));
     var commonPath = path.join(testDir, 'common.dart');
     var testCode = new File('$commonPath').readAsStringSync();
     var lib = initAnalyzer({'common.dart' : testCode})
         .libraryFor('common.dart');
-    var coreLib = lib.visibleLibraries.firstWhere(
-        (l) => l.displayName == 'dart.core');
     var generator = new SmokeCodeGenerator();
     var recorder = new Recorder(generator, _resolveImportUrl);
 
     lookupMember(String className, String memberName, bool recursive) {
       recorder.lookupMember(lib.getType(className), memberName,
           recursive: recursive, includeAccessors: false);
     }
 
     runQuery(String className, QueryOptions options) {
       recorder.runQuery(lib.getType(className), options,
@@ skipping 101 matching lines @@
       ..writeln('  common.main();')
       ..writeln('}');
   return sb.toString();
 }
 
 _resolveImportUrl(LibraryElement lib) {
   if (lib.isDartCore) return 'dart:core';
   if (lib.displayName == 'smoke.test.common') return 'common.dart';
   return 'unknown.dart';
 }