Move update state bits under changed branch

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 5149eaa3437e59c498823929f53b7e82cba9184a..71441175a6272bed1ff1adb33e1b560da9ba544f 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -2736,9 +2736,9 @@ void Class::DisableCHAOptimizedCode() {
 
 void Class::SetTraceAllocation(bool trace_allocation) const {
   const bool changed = trace_allocation != this->trace_allocation();
-  set_state_bits(
-      TraceAllocationBit::update(trace_allocation, raw_ptr()->state_bits_));
   if (changed) {
+    set_state_bits(
+        TraceAllocationBit::update(trace_allocation, raw_ptr()->state_bits_));
     Isolate* isolate = Isolate::Current();
     ClassTable* class_table = isolate->class_table();
     class_table->TraceAllocationsFor(id(), trace_allocation);