Provide API support for weak handles and post-mortem finalization.

runtime/vm/isolate.h

Index: runtime/vm/isolate.h
diff --git a/runtime/vm/isolate.h b/runtime/vm/isolate.h
index 402b0147298f54cc918abc124fcc9864eed8c979..f25e954424922a94035c6b852bbd66e9345ffe5c 100644
--- a/runtime/vm/isolate.h
+++ b/runtime/vm/isolate.h
@@ -18,6 +18,7 @@ class BigintStore;
 class CodeIndexTable;
 class Debugger;
 class HandleScope;
+class HandleVisitor;
 class Heap;
 class LongJump;
 class MessageQueue;
@@ -44,10 +45,7 @@ class Isolate {
   // Visit all object pointers.
   void VisitObjectPointers(ObjectPointerVisitor* visitor, bool validate_frames);
 
-  void VisitStrongObjectPointers(ObjectPointerVisitor* visitor,
-                                 bool validate_frames);
-
-  void VisitWeakObjectPointers(ObjectPointerVisitor* visitor);
+  void VisitWeakPersistentHandles(HandleVisitor* visitor);
 
   StoreBufferBlock* store_buffer() { return &store_buffer_; }