Fix expectations for co19 RegExp tests.

sdk/lib/_internal/compiler/implementation/lib/regexp_helper.dart

Index: sdk/lib/_internal/compiler/implementation/lib/regexp_helper.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/regexp_helper.dart b/sdk/lib/_internal/compiler/implementation/lib/regexp_helper.dart
index 1e6bc7bfcd5d8134e9554d0f40dfff60e6e3587c..45ab03c85aa57d738c66c9740c750559c7926247 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/regexp_helper.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/regexp_helper.dart
@@ -138,7 +138,7 @@ class _AllMatchesIterator implements Iterator<Match> {
     // hidden global flag.
     if (_current != null && _current.start == _current.end) {
       // Advance implicit start-position if last match was empty.
-      JS("void", "#.lastIndex++", _re._nativeRegExp);
+      JS("void", "#.lastIndex++", regExpGetNative(_re));
     }
     _current = _re.firstMatch(_str);
     return _current != null;