Provide ability to patch external functions in a class that has already been finalized. The follow…

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 8a818f64b0353bc2ddc39183286d0f73890a9f79..5f2692a08fd984cd28c61a39401bdf7412ae022a 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -1265,6 +1265,12 @@ class Class : public Object {
 
   void set_is_prefinalized() const;
 
+  bool is_refinalize_after_patch() const {
+    return ClassFinalizedBits::decode(raw_ptr()->state_bits_)
+        == RawClass::kRefinalizeAfterPatch;
+  }
+
+  void SetRefinalizeAfterPatch() const;
   void ResetFinalization() const;
 
   bool is_marked_for_parsing() const {
@@ -1378,6 +1384,8 @@ class Class : public Object {
   bool TraceAllocation(Isolate* isolate) const;
   void SetTraceAllocation(bool trace_allocation) const;
 
+  bool ValidatePostFinalizePatch(const Class& orig_class, Error* error) const;
+
  private:
   enum MemberKind {
     kAny = 0,