Fix asserts in StackFrameIterator which were effectively disabled

runtime/vm/simulator_arm.cc

Index: runtime/vm/simulator_arm.cc
diff --git a/runtime/vm/simulator_arm.cc b/runtime/vm/simulator_arm.cc
index c4170b84657ccda58c361bdf0c635a6ae7137a19..50cb88d0c5ba4ee39565654d328c0a745507d5c6 100644
--- a/runtime/vm/simulator_arm.cc
+++ b/runtime/vm/simulator_arm.cc
@@ -281,9 +281,10 @@ void SimulatorDebugger::PrintDartFrame(uword pc,
 
 
 void SimulatorDebugger::PrintBacktrace() {
-  StackFrameIterator frames(sim_->get_register(FP), sim_->get_register(SP),
-                            sim_->get_pc(),
-                            StackFrameIterator::kDontValidateFrames);
+  StackFrameIterator frames(
+      sim_->get_register(FP), sim_->get_register(SP), sim_->get_pc(),
+      StackFrameIterator::kDontValidateFrames, Thread::Current(),
+      StackFrameIterator::kNoCrossThreadIteration);
   StackFrame* frame = frames.NextFrame();
   ASSERT(frame != NULL);
   Function& function = Function::Handle();