Fix asserts in StackFrameIterator which were effectively disabled

runtime/vm/weak_code.cc

Index: runtime/vm/weak_code.cc
diff --git a/runtime/vm/weak_code.cc b/runtime/vm/weak_code.cc
index 544082644ef1cd6fabf049b05efd806ece516b9a..7f2f4064ff37f551baba76af68badef9dae5b39a 100644
--- a/runtime/vm/weak_code.cc
+++ b/runtime/vm/weak_code.cc
@@ -61,7 +61,8 @@ bool WeakCodeReferences::IsOptimizedCode(const Array& dependent_code,
 
 
 void WeakCodeReferences::DisableCode() {
-  const Array& code_objects = Array::Handle(array_.raw());
+  Thread* thread = Thread::Current();
+  const Array& code_objects = Array::Handle(thread->zone(), array_.raw());
   if (code_objects.IsNull()) {
     return;
   }
@@ -70,7 +71,8 @@ void WeakCodeReferences::DisableCode() {
   // Disable all code on stack.
   Code& code = Code::Handle();
   {
-    DartFrameIterator iterator;
+    DartFrameIterator iterator(thread,
+                               StackFrameIterator::kNoCrossThreadIteration);
     StackFrame* frame = iterator.NextFrame();
     while (frame != NULL) {
       code = frame->LookupDartCode();