Improve Observatory debugger behaviour when an isolate exits with unhandled exceptions

runtime/observatory/tests/service/pause_on_unhandled_exceptions_test.dart

Index: runtime/observatory/tests/service/pause_on_unhandled_exceptions_test.dart
diff --git a/runtime/observatory/tests/service/pause_on_unhandled_exceptions_test.dart b/runtime/observatory/tests/service/pause_on_unhandled_exceptions_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..4a6b2ddf2ac8656976fd7f6151a132bc987e6ab7
--- /dev/null
+++ b/runtime/observatory/tests/service/pause_on_unhandled_exceptions_test.dart
@@ -0,0 +1,27 @@
+// Copyright (c) 2015, 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.
+// VMOptions=--error_on_bad_type --error_on_bad_override
+
+import 'package:observatory/service_io.dart';
+import 'package:unittest/unittest.dart';
+import 'test_helper.dart';
+import 'dart:async';
+
+doThrow() {
+  throw "TheException"; // Line 13.
+  return "end of doThrow";
+}
+
+var tests = [
+  hasStoppedWithUnhandledException,
+  (Isolate isolate) async {
+    var stack = await isolate.getStack();
+    expect(stack['frames'][0].function.name, equals('doThrow'));
+  }
+];
+
+main(args) => runIsolateTests(args,
+                              tests,
+                              pause_on_unhandled_exceptions: true,
+                              testeeConcurrent: doThrow);