Compute [WorldImpact] for main method as entrypoint

pkg/compiler/lib/src/common/backend_api.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.
 
 library dart2js.backend_api;
 
 import 'dart:async' show Future;
 
 import '../common.dart';
 import '../common/codegen.dart' show CodegenImpact;
 import '../common/resolution.dart' show ResolutionImpact, Frontend, Target;
 import '../compile_time_constants.dart'
     show BackendConstantEnvironment, ConstantCompilerTask;
 import '../compiler.dart' show Compiler;
 import '../constants/constant_system.dart' show ConstantSystem;
 import '../constants/expressions.dart' show ConstantExpression;
 import '../constants/values.dart' show ConstantValue;
 import '../dart_types.dart' show DartType, InterfaceType;
 import '../elements/elements.dart'
-    show ClassElement, Element, FunctionElement, LibraryElement;
+    show ClassElement, Element, FunctionElement, MethodElement, LibraryElement;
 import '../enqueue.dart' show Enqueuer, EnqueueTask, ResolutionEnqueuer;
 import '../io/code_output.dart' show CodeBuffer;
 import '../io/source_information.dart' show SourceInformationStrategy;
 import '../js_backend/backend_helpers.dart' as js_backend show BackendHelpers;
 import '../js_backend/js_backend.dart' as js_backend;
 import '../library_loader.dart' show LibraryLoader, LoadedLibraries;
 import '../native/native.dart' as native show NativeEnqueuer, maybeEnableNative;
 import '../patch_parser.dart'
     show checkNativeAnnotation, checkJsInteropAnnotation;
 import '../serialization/serialization.dart'
@@ skipping 275 matching lines @@
   bool shouldOutput(Element element) => true;
 
   FunctionElement helperForBadMain() => null;
 
   FunctionElement helperForMissingMain() => null;
 
   FunctionElement helperForMainArity() => null;
 
   void forgetElement(Element element) {}
 
-  void registerMainHasArguments(Enqueuer enqueuer) {}
+  /// Computes the [WorldImpact] of calling [mainMethod] as the entry point.
+  WorldImpact computeMainImpact(Enqueuer enqueuer, MethodElement mainMethod) {}
 
   /// Returns the location of the patch-file associated with [libraryName]
   /// resolved from [plaformConfigUri].
   ///
   /// Returns null if there is none.
   Uri resolvePatchUri(String libraryName, Uri plaformConfigUri);
 
   /// Creates an impact strategy to use for compilation.
   ImpactStrategy createImpactStrategy(
       {bool supportDeferredLoad: true,
@@ skipping 67 matching lines @@
   ClassElement get typeImplementation;
   ClassElement get boolImplementation;
   ClassElement get nullImplementation;
   ClassElement get uint32Implementation;
   ClassElement get uint31Implementation;
   ClassElement get positiveIntImplementation;
   ClassElement get syncStarIterableImplementation;
   ClassElement get asyncFutureImplementation;
   ClassElement get asyncStarStreamImplementation;
 }