First step for modular output in fasta.

pkg/front_end/lib/compiler_options.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 front_end.compiler_options;
 
-import 'dart:async';
-
 import 'package:front_end/src/base/performace_logger.dart';
 import 'package:front_end/src/incremental/byte_store.dart';
 
 import 'compilation_error.dart';
 import 'file_system.dart';
 import 'physical_file_system.dart';
-import 'src/simple_error.dart';
 
 /// Default error handler used by [CompilerOptions.onError].
 void defaultErrorHandler(CompilationError error) => throw error;
 
 /// Callback used to report errors encountered during compilation.
 typedef void ErrorHandler(CompilationError error);
 
 /// Front-end options relevant to compiler back ends.
 ///
 /// Not intended to be implemented or extended by clients.
@@ skipping 117 matching lines @@
   /// either absolute or relative URIs. Absolute URIs are read directly, while
   /// relative URIs are resolved from the [sdkRoot].
   Map<Uri, List<Uri>> targetPatches = {};
 
   /// Additional core libraries to be loaded when building a program.
   // TODO(sigmund): delete. Ideally building a program only needs what's
   // reachable and we can use kernelForBuildUnit when creating a snapshot of the
   // SDK itself.
   List<Uri> additionalLibraries = [];
 }
-
-Future<bool> validateOptions(CompilerOptions options) async {
-  var fs = options.fileSystem;
-  var root = options.sdkRoot;
-
-  bool _report(String msg) {
-    options.onError(new SimpleError(msg));
-    return false;
-  }
-
-  if (root != null && !await fs.entityForUri(root).exists()) {
-    return _report("SDK root directory not found: ${options.sdkRoot}");
-  }
-
-  var summary = options.sdkSummary;
-  if (summary != null && !await fs.entityForUri(summary).exists()) {
-    return _report("SDK summary not found: ${options.sdkSummary}");
-  }
-
-  return true;
-}