1. Delete prolog weak persistent handles when shutting down an isolate

runtime/vm/object.h

Index: runtime/vm/object.h
===================================================================
--- runtime/vm/object.h	(revision 31790)
+++ runtime/vm/object.h	(working copy)
@@ -6087,10 +6087,6 @@
     return (ElementSizeInBytes(cid) * Length());
   }
 
-  void* GetPeer() const {
-    return raw_ptr()->peer_;
-  }
-
   void* DataAddr(intptr_t byte_offset) const {
     ASSERT((byte_offset == 0) ||
            ((byte_offset > 0) && (byte_offset < LengthInBytes())));
@@ -6170,10 +6166,6 @@
     raw_ptr()->data_ = data;
   }
 
-  void SetPeer(void* peer) const {
-    raw_ptr()->peer_ = peer;
-  }
-
  private:
   FINAL_HEAP_OBJECT_IMPLEMENTATION(ExternalTypedData, Instance);
   friend class Class;