Track loading happening in parallel with background compilation and abort compilation if necessary.

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index 7678eefbae743b2f8df4967203bafd2fa2aa5046..8d688b193e15fab5009beecc51909f0d3028fad1 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -815,11 +815,11 @@ Isolate::Isolate(const Dart_IsolateFlags& api_flags)
       metrics_list_head_(NULL),
       compilation_allowed_(true),
       all_classes_finalized_(false),
+      top_level_parsing_(false),
       next_(NULL),
       pause_loop_monitor_(NULL),
-      cha_invalidation_gen_(kInvalidGen),
       field_invalidation_gen_(kInvalidGen),
-      prefix_invalidation_gen_(kInvalidGen),
+      loading_invalidation_gen_(kInvalidGen),
       boxed_field_list_mutex_(new Mutex()),
       boxed_field_list_(GrowableObjectArray::null()),
       spawn_count_monitor_(new Monitor()),