fix first frame reporting logic (#3640)

packages/flutter/lib/src/widgets/binding.dart

@@ -206,7 +206,7 @@ abstract class WidgetsBinding extends BindingBase implements GestureBinding, Ren
     buildOwner.finalizeTree();
     // TODO(ianh): Following code should not be included in release mode, only profile and debug modes.
     if (_needToReportFirstFrame) {
-      if (_thisFrameWasUseful) {
+      if (!_thisFrameWasUseful) {
         _thisFrameWasUseful = true;
       } else {
         developer.Timeline.instantSync('Widgets completed first useful frame');