- reset 'dirty' flag to false after the libraries mirrors is computed, this ensures that we compute…

runtime/lib/mirrors_impl.dart

Index: runtime/lib/mirrors_impl.dart
diff --git a/runtime/lib/mirrors_impl.dart b/runtime/lib/mirrors_impl.dart
index 78835a43b3378ba6931dd9d9845d49daa20283a9..8fdd7ba751badb4ca6ed491b5ecca3680b6512ff 100644
--- a/runtime/lib/mirrors_impl.dart
+++ b/runtime/lib/mirrors_impl.dart
@@ -226,6 +226,7 @@ class _LocalMirrorSystem extends MirrorSystem {
     if ((_libraries == null) || dirty) {
       _libraries = new Map<Uri, LibraryMirror>.fromIterable(
           _computeLibraries(), key: (e) => e.uri);
+      dirty = false;
     }
     return _libraries;
   }