tracing: Make ConvertableToTraceFormat move-only scoped_ptr

cc/scheduler/scheduler_state_machine.cc

Index: cc/scheduler/scheduler_state_machine.cc
diff --git a/cc/scheduler/scheduler_state_machine.cc b/cc/scheduler/scheduler_state_machine.cc
index 23715ae6dd38b3a5629fe52881a9fa0a6c6747f5..13bf780f6b36fd97cd6439b9cd98af993b20e605 100644
--- a/cc/scheduler/scheduler_state_machine.cc
+++ b/cc/scheduler/scheduler_state_machine.cc
@@ -189,12 +189,11 @@ const char* SchedulerStateMachine::ActionToString(Action action) {
   return "???";
 }
 
-scoped_refptr<base::trace_event::ConvertableToTraceFormat>
+scoped_ptr<base::trace_event::ConvertableToTraceFormat>
 SchedulerStateMachine::AsValue() const {
-  scoped_refptr<base::trace_event::TracedValue> state =
-      new base::trace_event::TracedValue();
+  auto state = make_scoped_ptr(new base::trace_event::TracedValue);
   AsValueInto(state.get());
-  return state;
+  return std::move(state);
 }
 
 void SchedulerStateMachine::AsValueInto(