Strong mode cleaning of many dart2js tests.

tests/compiler/dart2js/serialization/compilation_test_helper.dart

 // Copyright (c) 2016, 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.
 
 library dart2js.serialization_compilation_test;
 
 import 'dart:async';
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/compiler_new.dart';
 import 'package:compiler/src/commandline_options.dart';
@@ skipping 16 matching lines @@
         await serializeDartCore(arguments: arguments);
     if (arguments.filename != null) {
       Uri entryPoint = Uri.base.resolve(nativeToUriPath(arguments.filename));
       SerializationResult result = await serialize(entryPoint,
           memorySourceFiles: serializedData.toMemorySourceFiles(),
           resolutionInputs: serializedData.toUris());
       await compile(entryPoint,
           resolutionInputs: result.serializedData.toUris(),
           sourceFiles: result.serializedData.toMemorySourceFiles());
     } else {
-      Uri entryPoint = Uri.parse('memory:main.dart');
       await arguments.forEachTest(serializedData, TESTS, compile);
     }
     printMeasurementResults();
   });
 }
 
 Future compile(Uri entryPoint,
     {Map<String, String> sourceFiles: const <String, String>{},
     List<Uri> resolutionInputs,
     int index,
@@ skipping 12 matching lines @@
         entryPoint: entryPoint,
         memorySourceFiles: sourceFiles,
         resolutionInputs: resolutionInputs,
         options: options,
         outputProvider: outputCollector);
   });
   if (verbose) {
     print(outputCollector.getOutput('', OutputType.js));
   }
 }