Revert "Allow stepping when paused at isolate start."

runtime/observatory/tests/service/pause_on_start_then_step_test.dart

-// 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=--compile_all --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';
-
-void testMain() {
-  print('Hello');
-  exit(0);
-}
-
-var tests = [
-
-(Isolate isolate) async {
-  Completer completer = new Completer();
-  var stream = await isolate.vm.getEventStream(VM.kDebugStream);
-  var subscription;
-  subscription = stream.listen((ServiceEvent event) {
-    if (event.kind == ServiceEvent.kPauseStart) {
-      print('Received PauseStart');
-      subscription.cancel();
-      completer.complete();
-    }
-  });
-
-  if (isolate.pauseEvent != null &&
-      isolate.pauseEvent.kind == ServiceEvent.kPauseStart) {
-    // Wait for the isolate to hit PauseStart.
-    subscription.cancel();
-  } else {
-    await completer.future;
-  }
-
-  completer = new Completer();
-  stream = await isolate.vm.getEventStream(VM.kDebugStream);
-  subscription = stream.listen((ServiceEvent event) {
-    if (event.kind == ServiceEvent.kPauseBreakpoint) {
-      print('Received PauseBreakpoint');
-      subscription.cancel();
-      completer.complete();
-    }
-  });
-
-  print('Stepping...');
-  isolate.stepInto();
-
-  // Wait for the isolate to hit PauseBreakpoint.
-  await completer.future;
-},
-
-];
-
-main(args) => runIsolateTests(args, tests,
-                              testeeConcurrent: testMain,
-                              pause_on_start: true, pause_on_exit: true);