Revert "Track the 'awaiter return' call stack..."

runtime/observatory/tests/service/pause_on_unhandled_async_exceptions2_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.
-// VMOptions=--error_on_bad_type --error_on_bad_override
-
-import 'package:observatory/service_io.dart';
-import 'package:observatory/models.dart' as M;
-import 'package:unittest/unittest.dart';
-import 'test_helper.dart';
-import 'service_test_common.dart';
-
-const LINE_A = 29;
-
-class Foo {
-
-}
-
-doThrow() {
-  throw "TheException"; // Line 13.
-  return "end of doThrow";
-}
-
-asyncThrower() async {
-  doThrow();
-}
-
-testeeMain() async {
-  // No try ... catch.
-  await asyncThrower();
-}
-
-var tests = [
-  hasStoppedWithUnhandledException,
-
-  (Isolate isolate) async {
-    print("We stoppped!");
-    var stack = await isolate.getStack();
-    expect(stack['asyncCausalFrames'], isNotNull);
-    var asyncStack = stack['asyncCausalFrames'];
-    expect(asyncStack[0].toString(), contains('doThrow'));
-    expect(asyncStack[1].toString(), contains('asyncThrower'));
-    expect(asyncStack[2].kind, equals(M.FrameKind.asyncSuspensionMarker));
-    expect(asyncStack[3].toString(), contains('testeeMain'));
-    // We've stopped at LINE_A.
-    expect(await asyncStack[3].location.toUserString(),
-           contains('.dart:$LINE_A'));
-  }
-];
-
-main(args) => runIsolateTests(args,
-                              tests,
-                              pause_on_unhandled_exceptions: true,
-                              testeeConcurrent: testeeMain);