tracing: Make ConvertableToTraceFormat move-only scoped_ptr

cc/playback/display_item_list.cc

Index: cc/playback/display_item_list.cc
diff --git a/cc/playback/display_item_list.cc b/cc/playback/display_item_list.cc
index be5b9d4aca902df2f90c163ae4079d5009457b2a..0162c86b80b38d5b125fffd297bca9372d56c10a 100644
--- a/cc/playback/display_item_list.cc
+++ b/cc/playback/display_item_list.cc
@@ -237,10 +237,9 @@ bool DisplayItemList::ShouldBeAnalyzedForSolidColor() const {
   return ApproximateOpCount() <= kOpCountThatIsOkToAnalyze;
 }
 
-scoped_refptr<base::trace_event::ConvertableToTraceFormat>
+scoped_ptr<base::trace_event::ConvertableToTraceFormat>
 DisplayItemList::AsValue(bool include_items) const {
-  scoped_refptr<base::trace_event::TracedValue> state =
-      new base::trace_event::TracedValue();
+  auto state = make_scoped_ptr(new base::trace_event::TracedValue);
 
   state->BeginDictionary("params");
   if (include_items) {
@@ -273,7 +272,7 @@ DisplayItemList::AsValue(bool include_items) const {
     state->SetString("skp64", b64_picture);
   }
 
-  return state;
+  return std::move(state);
 }
 
 void DisplayItemList::EmitTraceSnapshot() const {