Remove Compiler.mainApp and Compiler.mainFunction

tests/compiler/dart2js/mock_compiler.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 mock_compiler;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:compiler/compiler_new.dart' as api;
@@ skipping 49 matching lines @@
 
   /// Expected number of errors. If `null`, the number of errors is not checked.
   final int expectedErrors;
   final Map<String, SourceFile> sourceFiles;
   Node parsedTree;
   final LibrarySourceProvider librariesOverride;
   final DiagnosticCollector diagnosticCollector = new DiagnosticCollector();
   final ResolvedUriTranslator resolvedUriTranslator =
       new MockResolvedUriTranslator();
   final Measurer measurer = new Measurer();
+  LibraryElement mainApp;
 
   MockCompiler.internal(
       {Map<String, String> coreSource,
       bool enableTypeAssertions: false,
       bool enableUserAssertions: false,
       bool enableMinification: false,
       bool disableTypeInference: false,
       bool analyzeAll: false,
       bool analyzeOnly: false,
       bool preserveComments: false,
@@ skipping 314 matching lines @@
       trustTypeAnnotations: trustTypeAnnotations,
       enableTypeAssertions: enableTypeAssertions,
       enableUserAssertions: enableUserAssertions,
       expectedErrors: expectedErrors,
       expectedWarnings: expectedWarnings,
       outputProvider: outputProvider);
   compiler.registerSource(uri, code);
   compiler.diagnosticHandler = createHandler(compiler, code);
   return compiler;
 }