Implement rewind on all platforms except for dbc.

runtime/observatory/tests/service/service_test_common.dart

Index: runtime/observatory/tests/service/service_test_common.dart
diff --git a/runtime/observatory/tests/service/service_test_common.dart b/runtime/observatory/tests/service/service_test_common.dart
index bf1d013c5d89c9c8d0e54ebac8802431b161ef11..45e8b46c9e6248a00652859619c15422e28d0fa1 100644
--- a/runtime/observatory/tests/service/service_test_common.dart
+++ b/runtime/observatory/tests/service/service_test_common.dart
@@ -234,6 +234,10 @@ IsolateTest stoppedAtLine(int line) {
   return (Isolate isolate) async {
     print("Checking we are at line $line");
 
+    // Make sure that the isolate has stopped.
+    isolate.reload();
+    expect(isolate.pauseEvent is! M.ResumeEvent, isTrue);
+
     ServiceMap stack = await isolate.getStack();
     expect(stack.type, equals('Stack'));