Compute [WorldImpact] for main method as entrypoint

tests/compiler/dart2js/resolver_test.dart

 // Copyright (c) 2012, 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 'dart:async';
 import 'dart:collection';
 
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
 import 'package:compiler/src/constants/expressions.dart';
@@ skipping 223 matching lines @@
   });
 }
 
 Future testSwitch() {
   return MockCompiler.create((MockCompiler compiler) {
     compiler.parseScript("class Foo { foo() {"
         "switch (null) { case '': break; case 2: break; } } }");
     compiler.resolveStatement("Foo foo;");
     ClassElement fooElement = compiler.mainApp.find("Foo");
     FunctionElement funElement = fooElement.lookupLocalMember("foo");
-    compiler.processQueue(compiler.enqueuer.resolution, funElement);
+    compiler.enqueuer.resolution.addToWorkList(funElement);
+    compiler.processQueue(compiler.enqueuer.resolution, null);
     DiagnosticCollector collector = compiler.diagnosticCollector;
     Expect.equals(0, collector.warnings.length);
     Expect.equals(1, collector.errors.length);
     Expect.equals(MessageKind.SWITCH_CASE_TYPES_NOT_EQUAL,
         collector.errors.first.message.kind);
     Expect.equals(2, collector.infos.length);
     Expect.equals(MessageKind.SWITCH_CASE_TYPES_NOT_EQUAL_CASE,
         collector.infos.first.message.kind);
     Expect.equals(MessageKind.SWITCH_CASE_TYPES_NOT_EQUAL_CASE,
         collector.infos.elementAt(1).message.kind);
@@ skipping 1275 matching lines @@
       functionName: 'm');
   check(
       '''
     class A {
       m() => () => await - 3;
     }
     main() => new A().m();
   ''',
       className: 'A');
 }