[kernel] Add offset to SwitchContinueStatement; add debugging test

runtime/observatory/tests/service/step_through_switch_with_continue_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.
+
+import 'test_helper.dart';
+import 'service_test_common.dart';
+
+const int LINE = 11;
+const String file = "step_through_switch_with_continue_test.dart";
+
+code() {
+  switch (switchOnMe.length) {
+    case 0:
+      print("(got 0!");
+      continue label;
+    label:
+    case 1:
+      print("Got 0 or 1!");
+      break;
+    case 2:
+      print("Got 2!");
+      break;
+    default:
+      print("Got lost!");
+  }
+}
+
+List<String> switchOnMe = [];
+List<String> stops = [];
+List<String> expected = [
+  "$file:${LINE+0}:5", // after 'code'
+
+  "$file:${LINE+1}:11", // on switchOnMe
+  "$file:${LINE+1}:22", // on length
+
+  "$file:${LINE+2}:10", // on 0
+  "$file:${LINE+3}:7", // on print
+  "$file:${LINE+4}:7", // on continue
+
+  "$file:${LINE+7}:7", // on print
+  "$file:${LINE+8}:7", // on break
+
+  "$file:${LINE+15}:1" // on ending '}'
+];
+
+var tests = [
+  hasPausedAtStart,
+  setBreakpointAtLine(LINE),
+  runStepIntoThroughProgramRecordingStops(stops),
+  checkRecordedStops(stops, expected,
+      debugPrint: true, debugPrintFile: file, debugPrintLine: LINE)
+];
+
+main(args) {
+  runIsolateTestsSynchronous(args, tests,
+      testeeConcurrent: code, pause_on_start: true, pause_on_exit: true);
+}