Test showing crash when stepping through new Map creation.

runtime/observatory/tests/service/step_test.dart

Index: runtime/observatory/tests/service/step_test.dart
diff --git a/runtime/observatory/tests/service/step_test.dart b/runtime/observatory/tests/service/step_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..47009dc490aba26ec85107030121a4faa2f76809
--- /dev/null
+++ b/runtime/observatory/tests/service/step_test.dart
@@ -0,0 +1,38 @@
+import 'dart:async';
+import 'test_helper.dart';
+import 'service_test_common.dart';
+import 'package:observatory/service_io.dart';
+import 'package:unittest/unittest.dart';
+
+const int LINE_A = 10;
+
+code() {
+  var x = {}; // LINE_A
+}
+
+Future<Isolate> stepThroughProgram(Isolate isolate) async {
+  Completer completer = new Completer();
+  int pauseEventsSeen = 0;
+
+  await subscribeToStream(isolate.vm, VM.kDebugStream,
+      (ServiceEvent event) async {
+    if (event.kind == ServiceEvent.kPauseBreakpoint) {
+      // We are paused: Step further.
+      pauseEventsSeen++;
+      isolate.stepInto();
+    } else if (event.kind == ServiceEvent.kPauseExit) {
+      // We are at the exit: The test is done.
+      expect(pauseEventsSeen > 20, true,
+          reason: "Saw only $pauseEventsSeen pause events.");
+      await cancelStreamSubscription(VM.kDebugStream);
+      completer.complete();
+    }
+  });
+  isolate.resume();
+  return completer.future;
+}
+
+var tests = [hasPausedAtStart, setBreakpointAtLine(LINE_A), stepThroughProgram];
+
+main(args) => runIsolateTestsSynchronous(args, tests,
+    testeeConcurrent: code, pause_on_start: true, pause_on_exit: true);