Remove Compiler.mainApp and Compiler.mainFunction

tests/compiler/dart2js/kernel/impact_test.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.kernel.impact_test;
 
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/common.dart';
 import 'package:compiler/src/common/names.dart';
 import 'package:compiler/src/common/resolution.dart';
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/constants/expressions.dart';
 import 'package:compiler/src/elements/elements.dart';
+import 'package:compiler/src/elements/entities.dart';
 import 'package:compiler/src/elements/resolution_types.dart';
 import 'package:compiler/src/js_backend/backend.dart';
 import 'package:compiler/src/kernel/element_map.dart';
 import 'package:compiler/src/kernel/element_map_impl.dart';
 import 'package:compiler/src/resolution/registry.dart';
 import 'package:compiler/src/resolution/tree_elements.dart';
 import 'package:compiler/src/ssa/kernel_impact.dart';
 import 'package:compiler/src/serialization/equivalence.dart';
 import 'package:compiler/src/universe/call_structure.dart';
 import 'package:compiler/src/universe/feature.dart';
@@ skipping 716 matching lines @@
           Flags.useKernel,
           Flags.enableAssertMessage
         ]);
     compiler.resolution.retainCachesForTesting = true;
     Expect.isTrue(await compiler.run(entryPoint));
     JavaScriptBackend backend = compiler.backend;
     KernelToElementMapImpl kernelElementMap =
         new KernelToElementMapImpl(compiler.reporter, compiler.environment);
     kernelElementMap.addProgram(backend.kernelTask.program);
 
-    checkLibrary(compiler, kernelElementMap, compiler.mainApp,
-        fullTest: fullTest);
-    compiler.libraryLoader.libraries.forEach((library) {
-      if (library == compiler.mainApp) return;
+    LibraryElement mainApp =
+        compiler.frontendStrategy.elementEnvironment.mainLibrary;
+    checkLibrary(compiler, kernelElementMap, mainApp, fullTest: fullTest);
+    compiler.libraryLoader.libraries.forEach((LibraryEntity library) {
+      if (library == mainApp) return;
       checkLibrary(compiler, kernelElementMap, library, fullTest: fullTest);
     });
   });
 }
 
 void checkLibrary(Compiler compiler, KernelToElementMapMixin elementMap,
     LibraryElement library,
     {bool fullTest: false}) {
   library.forEachLocalMember((_element) {
     AstElement element = _element;
@@ skipping 135 matching lines @@
         builder.registerFeature(Feature.THROW_EXPRESSION);
         break;
       default:
         builder.registerFeature(feature);
         break;
     }
   }
   impact.nativeData.forEach(builder.registerNativeData);
   return builder;
 }