Check compiler exitCode.

sdk/lib/_internal/compiler/implementation/util/util.dart

 // Copyright (c) 2011, 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.util;
 
 import "dart:collection";
 import 'util_implementation.dart';
 import 'characters.dart';
 
@@ skipping 272 matching lines @@
   }
   buffer.write(string);
 }
 
 int computeHashCode(part1, [part2, part3, part4]) {
   return (part1.hashCode
           ^ part2.hashCode
           ^ part3.hashCode
           ^ part4.hashCode) & 0x3fffffff;
 }
+
+/// Exception to flag that the compiler has crashed when the error and stack
+/// trace have been reported.
+class CompilerCrashedException implements Exception {
+  final String reason;
+  CompilerCrashedException(this.reason);
+
+  String toString() {
+    String banner = 'Compiler crashed';
+    return (reason != null) ? '$banner: $reason' : '$banner';
+  }
+}