update constructor

lib/ui/hooks.dart

@@ -200,7 +200,7 @@ void _reportTimings(List<int> timings) {
   assert(timings.length % FramePhase.values.length == 0);
   final List<FrameTiming> frameTimings = <FrameTiming>[];
   for (int i = 0; i < timings.length; i += FramePhase.values.length) {
-    frameTimings.add(FrameTiming(timings.sublist(i, i + FramePhase.values.length)));
+    frameTimings.add(FrameTiming._(timings.sublist(i, i + FramePhase.values.length)));
   }
   _invoke1(window.onReportTimings, window._onReportTimingsZone, frameTimings);
 }

lib/ui/window.dart

@@ -87,14 +87,34 @@ enum FramePhase {
 /// Therefore it's recommended to only monitor and analyze performance metrics
 /// in profile and release modes.
 class FrameTiming {
+  /// Construct [FrameTiming] with raw timestamps in microseconds.
+  ///
+  /// This constructor is used for unit test only. Real [FrameTiming]s should
+  /// be retrieved from [Window.onReportTimings].
+  factory FrameTiming({
+    required int vsyncStart,
+    required int buildStart,
+    required int buildFinish,
+    required int rasterStart,
+    required int rasterFinish,
+  }) {
+    return FrameTiming._(<int>[
+      vsyncStart,
+      buildStart,
+      buildFinish,
+      rasterStart,
+      rasterFinish
+    ]);
+  }
+
   /// Construct [FrameTiming] with raw timestamps in microseconds.
   ///
   /// List [timestamps] must have the same number of elements as
   /// [FramePhase.values].
   ///
   /// This constructor is usually only called by the Flutter engine, or a test.
   /// To get the [FrameTiming] of your app, see [Window.onReportTimings].
-  FrameTiming(List<int> timestamps)
+  FrameTiming._(List<int> timestamps)
       : assert(timestamps.length == FramePhase.values.length), _timestamps = timestamps;
 
   /// Construct [FrameTiming] with given timestamp in micrseconds.
@@ -111,7 +131,9 @@ class FrameTiming {
     required int rasterStart,
     required int rasterFinish
   }) {
-    return FrameTiming(<int>[
+    return FrameTiming._(<int>[
+      // This is for temporarily backward compatiblilty.
+      vsyncStart ?? buildStart,
       buildStart,
       buildFinish,
       rasterStart,

lib/web_ui/lib/src/ui/window.dart

@@ -1040,16 +1040,35 @@ enum FramePhase {
 /// Therefore it's recommended to only monitor and analyze performance metrics
 /// in profile and release modes.
 class FrameTiming {
+  /// Construct [FrameTiming] with raw timestamps in microseconds.
+  ///
+  /// This constructor is used for unit test only. Real [FrameTiming]s should
+  /// be retrieved from [Window.onReportTimings].
+  factory FrameTiming({
+    required int vsyncStart,
+    required int buildStart,
+    required int buildFinish,
+    required int rasterStart,
+    required int rasterFinish,
+  }) {
+    return FrameTiming._(<int>[
+      vsyncStart,
+      buildStart,
+      buildFinish,
+      rasterStart,
+      rasterFinish
+    ]);
+  }
+
   /// Construct [FrameTiming] with raw timestamps in microseconds.
   ///
   /// List [timestamps] must have the same number of elements as
   /// [FramePhase.values].
   ///
   /// This constructor is usually only called by the Flutter engine, or a test.
   /// To get the [FrameTiming] of your app, see [Window.onReportTimings].
-  FrameTiming(List<int> timestamps)
-      : assert(timestamps.length == FramePhase.values.length),
-        _timestamps = timestamps;
+  FrameTiming._(List<int> timestamps)
+      : assert(timestamps.length == FramePhase.values.length), _timestamps = timestamps;
 
   /// Construct [FrameTiming] with given timestamp in micrseconds.
   ///
@@ -1058,13 +1077,22 @@ class FrameTiming {
   ///
   /// TODO(CareF): This is part of #20229. Remove back to default constructor
   /// after #20229 lands and corresponding framwork PRs land.
-  FrameTiming.fromTimeStamps({
+  factory FrameTiming.fromTimeStamps({
     int? vsyncStart,
     required int buildStart,
     required int buildFinish,
     required int rasterStart,
     required int rasterFinish
-  }) : _timestamps = <int>[buildStart, buildFinish, rasterStart, rasterFinish];
+  }) {
+    return FrameTiming._(<int>[
+      // This is for temporarily backward compatiblilty.
+      vsyncStart ?? buildStart,
+      buildStart,
+      buildFinish,
+      rasterStart,
+      rasterFinish
+    ]);
+  }
 
   /// This is a raw timestamp in microseconds from some epoch. The epoch in all
   /// [FrameTiming] is the same, but it may not match [DateTime]'s epoch.

testing/dart/window_test.dart

@@ -22,7 +22,13 @@ void main() {
   });
 
   test('FrameTiming.toString has the correct format', () {
-    final FrameTiming timing = FrameTiming(<int>[500, 1000, 8000, 9000, 19500]);
+    final FrameTiming timing = FrameTiming(
+      vsyncStart: 500,
+      buildStart: 1000,
+      buildFinish: 8000,
+      rasterStart: 9000,
+      rasterFinish: 19500
+    );
     expect(timing.toString(), 'FrameTiming(buildDuration: 7.0ms, rasterDuration: 10.5ms, vsyncOverhead: 0.5ms, totalSpan: 19.0ms)');
   });