Pass in the isolate parameter to the weak persistent callback handler so that

runtime/vm/scavenger.cc

Index: runtime/vm/scavenger.cc
===================================================================
--- runtime/vm/scavenger.cc	(revision 33281)
+++ runtime/vm/scavenger.cc	(working copy)
@@ -271,7 +271,9 @@
 
 class ScavengerWeakVisitor : public HandleVisitor {
  public:
-  explicit ScavengerWeakVisitor(Scavenger* scavenger) : scavenger_(scavenger) {
+  explicit ScavengerWeakVisitor(Scavenger* scavenger)
+      :  HandleVisitor(Isolate::Current()),
+         scavenger_(scavenger) {
   }
 
   void VisitHandle(uword addr, bool is_prologue_weak) {
@@ -279,7 +281,9 @@
         reinterpret_cast<FinalizablePersistentHandle*>(addr);
     RawObject** p = handle->raw_addr();
     if (scavenger_->IsUnreachable(p)) {
-      FinalizablePersistentHandle::Finalize(handle, is_prologue_weak);
+      FinalizablePersistentHandle::Finalize(isolate(),
+                                            handle,
+                                            is_prologue_weak);
     }
   }