Fix asserts in StackFrameIterator which were effectively disabled

runtime/vm/deopt_instructions.cc

Index: runtime/vm/deopt_instructions.cc
diff --git a/runtime/vm/deopt_instructions.cc b/runtime/vm/deopt_instructions.cc
index 1c6f754176fc5fff18fb28a6121ca76017768938..d50513c79dca2c09b8027e55c858ee0da1d247cd 100644
--- a/runtime/vm/deopt_instructions.cc
+++ b/runtime/vm/deopt_instructions.cc
@@ -416,7 +416,8 @@ intptr_t DeoptContext::MaterializeDeferredObjects() {
   // Since this is the only step where GC can occur during deoptimization,
   // use it to report the source line where deoptimization occured.
   if (FLAG_trace_deoptimization || FLAG_trace_deoptimization_verbose) {
-    DartFrameIterator iterator;
+    DartFrameIterator iterator(Thread::Current(),
+                               StackFrameIterator::kNoCrossThreadIteration);
     StackFrame* top_frame = iterator.NextFrame();
     ASSERT(top_frame != NULL);
     const Code& code = Code::Handle(top_frame->LookupDartCode());