Make some VM libraries patch cleanly using the analyzer.

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index c5abb5ae42dd0318bb2a0e5fbbaa18abc30dc002..27ffbd0d502200974a7049ec351114794c73021e 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -5860,7 +5860,7 @@ DART_EXPORT Dart_Handle Dart_FinalizeLoading(bool complete_futures) {
     // Notify mirrors that MirrorSystem.libraries needs to be recomputed.
     const Library& libmirrors = Library::Handle(Z, Library::MirrorsLibrary());
     const Field& dirty_bit = Field::Handle(
-        Z, libmirrors.LookupLocalField(String::Handle(String::New("dirty"))));
+        Z, libmirrors.LookupLocalField(String::Handle(String::New("_dirty"))));
     ASSERT(!dirty_bit.IsNull() && dirty_bit.is_static());
     dirty_bit.SetStaticValue(Bool::True());
   }