Support loading binary data in dart2js

tests/compiler/dart2js/dill_loader_test.dart

 // Copyright (c) 2017, 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:io';
 import 'memory_compiler.dart';
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/common_elements.dart';
 import 'package:compiler/src/diagnostics/spannable.dart' show Spannable;
 import 'package:compiler/src/elements/entities.dart'
     show LibraryEntity, ClassEntity;
+import 'package:compiler/src/io/source_file.dart' show Binary;
 import 'package:compiler/src/library_loader.dart' show ScriptLoader;
 import 'package:compiler/src/script.dart' show Script;
 import 'package:compiler/src/apiimpl.dart' show CompilerImpl;
 import "package:expect/expect.dart";
 import 'package:path/path.dart' as path;
 
 final String dartkExecutable = Platform.isWindows
     ? 'tools/dartk_wrappers/dartk.bat'
     : 'tools/dartk_wrappers/dartk';
 
 /// Run the dartk.dart script, and return the binary encoded results.
 List<int> runDartk(String filename) {
   String basePath = path.fromUri(Uri.base);
   String dartkPath = path.normalize(path.join(basePath, dartkExecutable));
 
   var args = [filename, '-fbin', '-ostdout'];
   ProcessResult result = Process.runSync(dartkPath, args, stdoutEncoding: null);
   Expect.equals(0, result.exitCode, result.stderr);
   return result.stdout;
 }
 
 class TestScriptLoader implements ScriptLoader {
   CompilerImpl compiler;
   TestScriptLoader(this.compiler);
 
   Future<Script> readScript(Uri uri, [Spannable spannable]) =>
       compiler.readScript(uri, spannable);
+
+  Future<Binary> readBinary(Uri uri, [Spannable spannable]) =>
+      compiler.readBinary(uri, spannable);
 }
 
 /// Test that the compiler can successfully read in .dill kernel files rather
 /// than just string source files.
 main() {
   asyncTest(() async {
     String filename = 'tests/corelib/list_literal_test.dart';
     Uri uri = Uri.base.resolve(filename);
     DiagnosticCollector diagnostics = new DiagnosticCollector();
     OutputCollector output = new OutputCollector();
@@ skipping 14 matching lines @@
 
     ElementEnvironment environment = compiler.elementEnvironment;
     LibraryEntity library = environment.lookupLibrary(uri);
     Expect.isNotNull(library);
     ClassEntity clss = environment.lookupClass(library, 'ListLiteralTest');
     Expect.isNotNull(clss);
     var member = environment.lookupClassMember(clss, 'testMain');
     Expect.isNotNull(member);
   });
 }