Remove unnecessary imports

Author: crackedhandle

packages/devtools_app/test/screens/performance/performance_screen_test.dart

@@ -9,9 +9,7 @@ import 'dart:async';
 
 import 'package:devtools_app/devtools_app.dart';
 import 'package:devtools_app/src/screens/performance/panes/controls/performance_controls.dart';
-import 'package:devtools_app/src/screens/performance/panes/flutter_frames/flutter_frame_model.dart';
 import 'package:devtools_app/src/screens/performance/panes/rebuild_stats/rebuild_stats.dart';
-import 'package:devtools_app/src/screens/performance/panes/rebuild_stats/rebuild_stats_model.dart';
 import 'package:devtools_app/src/screens/performance/panes/timeline_events/timeline_events_view.dart';
 import 'package:devtools_app/src/screens/performance/tabbed_performance_view.dart';
 import 'package:devtools_app/src/shared/feature_flags.dart';
@@ -21,7 +19,6 @@ import 'package:devtools_app_shared/utils.dart';
 import 'package:devtools_shared/devtools_test_utils.dart';
 import 'package:devtools_test/devtools_test.dart';
 import 'package:devtools_test/helpers.dart';
-import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_markdown/flutter_markdown.dart';
 import 'package:flutter_test/flutter_test.dart';