Remove Compiler.mainApp and Compiler.mainFunction

pkg/compiler/lib/src/js_backend/backend.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 js_backend.backend;
 
 import '../common.dart';
 import '../common/backend_api.dart'
     show ForeignResolver, NativeRegistry, ImpactTransformer;
 import '../common/codegen.dart' show CodegenWorkItem;
@@ skipping 951 matching lines @@
   int assembleProgram(ClosedWorld closedWorld) {
     int programSize = emitter.assembleProgram(namer, closedWorld);
     noSuchMethodRegistry.emitDiagnostic(reporter);
     int totalMethodCount = generatedCode.length;
     // TODO(johnniwinther): Support `preMirrorsMethodCount` for entities.
     if (mirrorsCodegenAnalysis.preMirrorsMethodCount != null &&
         totalMethodCount != mirrorsCodegenAnalysis.preMirrorsMethodCount) {
       int mirrorCount =
           totalMethodCount - mirrorsCodegenAnalysis.preMirrorsMethodCount;
       double percentage = (mirrorCount / totalMethodCount) * 100;
-      DiagnosticMessage hint =
-          reporter.createMessage(compiler.mainApp, MessageKind.MIRROR_BLOAT, {
+      DiagnosticMessage hint = reporter.createMessage(
+          closedWorld.elementEnvironment.mainLibrary,
+          MessageKind.MIRROR_BLOAT, {
         'count': mirrorCount,
         'total': totalMethodCount,
         'percentage': percentage.round()
       });
 
       List<DiagnosticMessage> infos = <DiagnosticMessage>[];
       for (LibraryElement library in compiler.libraryLoader.libraries) {
         if (library.isInternalLibrary) continue;
         for (ImportElement import in library.imports) {
           LibraryElement importedLibrary = import.importedLibrary;
@@ skipping 409 matching lines @@
 
   bool canUseAliasedSuperMember(MemberEntity member, Selector selector) {
     return !selector.isGetter;
   }
 
   /// Returns `true` if [member] is called from a subclass via `super`.
   bool isAliasedSuperMember(MemberEntity member) {
     return _aliasedSuperMembers.contains(member);
   }
 }