Add NosafepointScope and remove comment.

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 143cf9e409ac4647df55b2b7b58f3ad3ea61cb2e..4dcade6c39e0b0a554092e1c31455df1c2041889 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -8531,9 +8531,7 @@ RawClass* Object::clazz() const {
 
 
 DART_FORCE_INLINE void Object::SetRaw(RawObject* value) {
-  // NOTE: The assignment "raw_ = value" should be the first statement in
-  // this function. Also do not use 'value' in this function after the
-  // assignment (use 'raw_' instead).
+  NoSafepointScope no_safepoint_scope;
   raw_ = value;
   if ((reinterpret_cast<uword>(value) & kSmiTagMask) == kSmiTag) {
     set_vtable(Smi::handle_vtable_);