Refactor 'dart:profiler' UserTag API

runtime/lib/profiler.cc

Index: runtime/lib/profiler.cc
diff --git a/runtime/lib/profiler.cc b/runtime/lib/profiler.cc
index 75bf2d1ff768f29abb15c6b59d8ff774fbb6eacf..3128fb98194ed905be179c2088f90acc9ce9db71 100644
--- a/runtime/lib/profiler.cc
+++ b/runtime/lib/profiler.cc
@@ -36,28 +36,26 @@ DEFINE_NATIVE_ENTRY(UserTag_makeCurrent, 1) {
   if (FLAG_trace_intrinsified_natives) {
     OS::Print("UserTag_makeCurrent: %s\n", self.ToCString());
   }
+  const UserTag& old = UserTag::Handle(isolate->current_tag());
   self.MakeActive();
-  return Object::null();
+  return old.raw();
 }
 
 
-DEFINE_NATIVE_ENTRY(Profiler_getCurrentTag, 0) {
+DEFINE_NATIVE_ENTRY(UserTag_defaultTag, 0) {
   if (FLAG_trace_intrinsified_natives) {
-    OS::Print("Profiler_getCurrentTag\n");
+    OS::Print("UserTag_defaultTag\n");
   }
-  return isolate->current_tag();
+  return isolate->object_store()->default_tag();
 }
 
 
-DEFINE_NATIVE_ENTRY(Profiler_clearCurrentTag, 0) {
-  // Use a NoGCScope to avoid creating a handle for the old current.
-  NoGCScope no_gc;
-  RawUserTag* old_current = isolate->current_tag();
-  UserTag::ClearActive();
+DEFINE_NATIVE_ENTRY(Profiler_getCurrentTag, 0) {
   if (FLAG_trace_intrinsified_natives) {
-    OS::Print("Profiler_clearCurrentTag\n");
+    OS::Print("Profiler_getCurrentTag\n");
   }
-  return old_current;
+  return isolate->current_tag();
 }
 
+
 }  // namespace dart