Check compiler exitCode.

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

Index: sdk/lib/_internal/compiler/implementation/util/util.dart
diff --git a/sdk/lib/_internal/compiler/implementation/util/util.dart b/sdk/lib/_internal/compiler/implementation/util/util.dart
index dee467d8f5e783c5451eb7e0839a49d7b1d1efe5..f307f64738a280f3139a9d2f364a93752892359f 100644
--- a/sdk/lib/_internal/compiler/implementation/util/util.dart
+++ b/sdk/lib/_internal/compiler/implementation/util/util.dart
@@ -290,3 +290,15 @@ int computeHashCode(part1, [part2, part3, part4]) {
           ^ 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';
+  }
+}