Debug garbage collector does not correctly remove cross-gen garbage

runtime/vm/heap.h

Index: runtime/vm/heap.h
diff --git a/runtime/vm/heap.h b/runtime/vm/heap.h
index 1c9968660d3b4a96ce05df568205a7735f400f81..87e209ae5f9b11c2eb990e7000431a77ee538078 100644
--- a/runtime/vm/heap.h
+++ b/runtime/vm/heap.h
@@ -306,6 +306,7 @@ class Heap {
   // ensure thread-safety.
   bool VerifyGC(MarkExpectation mark_expectation = kForbidMarked) const;
 
+
   // Helper functions for garbage collection.
   void CollectNewSpaceGarbage(Thread* thread,
                               ApiCallbacks api_callbacks,
@@ -313,6 +314,7 @@ class Heap {
   void CollectOldSpaceGarbage(Thread* thread,
                               ApiCallbacks api_callbacks,
                               GCReason reason);
+  void EvacuateNewSpace(Thread* thread, GCReason reason);
 
   // GC stats collection.
   void RecordBeforeGC(Space space, GCReason reason);