plumb frame number through to framework

common/settings.h

@@ -40,8 +40,14 @@ class FrameTiming {
     return data_[phase] = value;
   }
 
+  int64_t GetFrameNumber() const { return frame_number_; }
+  void SetFrameNumber(int64_t frame_number) {
+    frame_number_ = frame_number;
+  }
+
  private:
   fml::TimePoint data_[kCount];
+  int64_t frame_number_;
 };
 
 using TaskObserverAdd =

flow/frame_timings.cc

@@ -101,6 +101,7 @@ FrameTiming FrameTimingsRecorder::RecordRasterEnd(fml::TimePoint raster_end) {
   timing.Set(FrameTiming::kBuildFinish, build_end_);
   timing.Set(FrameTiming::kRasterStart, raster_start_);
   timing.Set(FrameTiming::kRasterFinish, raster_end_);
+  timing.SetFrameNumber(GetFrameNumber());
   return timing;
 }
 

flow/frame_timings_recorder_unittests.cc

@@ -53,10 +53,11 @@ TEST(FrameTimingsRecorderTest, RecordRasterTimes) {
   const auto raster_start = fml::TimePoint::Now();
   const auto raster_end = raster_start + fml::TimeDelta::FromMillisecondsF(16);
   recorder->RecordRasterStart(raster_start);
-  recorder->RecordRasterEnd(raster_end);
+  const auto timing = recorder->RecordRasterEnd(raster_end);
 
   ASSERT_EQ(raster_start, recorder->GetRasterStartTime());
   ASSERT_EQ(raster_end, recorder->GetRasterEndTime());
+  ASSERT_EQ(recorder->GetFrameNumber(), timing.GetFrameNumber());
 }
 
 // Windows and Fuchsia don't allow testing with killed by signal.

lib/ui/platform_dispatcher.dart

@@ -433,10 +433,10 @@ class PlatformDispatcher {
 
   // Called from the engine, via hooks.dart
   void _reportTimings(List<int> timings) {
-    assert(timings.length % FramePhase.values.length == 0);
+    assert(timings.length % (FramePhase.values.length + 1) == 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)));
+    for (int i = 0; i < timings.length; i += FramePhase.values.length + 1) {
+      frameTimings.add(FrameTiming._(timings.sublist(i, i + FramePhase.values.length + 1)));
     }
     _invoke1(onReportTimings, _onReportTimingsZone, frameTimings);
   }
@@ -1145,19 +1145,23 @@ class FrameTiming {
   ///
   /// This constructor is used for unit test only. Real [FrameTiming]s should
   /// be retrieved from [PlatformDispatcher.onReportTimings].
+  ///
+  /// If the [frameNumber] is not provided, it defaults to `-1`.
   factory FrameTiming({
     required int vsyncStart,
     required int buildStart,
     required int buildFinish,
     required int rasterStart,
     required int rasterFinish,
+    int frameNumber = -1,
   }) {
     return FrameTiming._(<int>[
       vsyncStart,
       buildStart,
       buildFinish,
       rasterStart,
-      rasterFinish
+      rasterFinish,
+      frameNumber,
     ]);
   }
 
@@ -1169,7 +1173,7 @@ class FrameTiming {
   /// This constructor is usually only called by the Flutter engine, or a test.
   /// To get the [FrameTiming] of your app, see [PlatformDispatcher.onReportTimings].
   FrameTiming._(this._timestamps)
-      : assert(_timestamps.length == FramePhase.values.length);
+      : assert(_timestamps.length == FramePhase.values.length + 1);
 
   /// 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.
@@ -1214,13 +1218,16 @@ class FrameTiming {
   /// See also [vsyncOverhead], [buildDuration] and [rasterDuration].
   Duration get totalSpan => _rawDuration(FramePhase.rasterFinish) - _rawDuration(FramePhase.vsyncStart);
 
+  /// The frame key associated with this frame measurement.
+  int get frameNumber => _timestamps.last;
+
   final List<int> _timestamps;  // in microseconds
 
   String _formatMS(Duration duration) => '${duration.inMicroseconds * 0.001}ms';
 
   @override
   String toString() {
-    return '$runtimeType(buildDuration: ${_formatMS(buildDuration)}, rasterDuration: ${_formatMS(rasterDuration)}, vsyncOverhead: ${_formatMS(vsyncOverhead)}, totalSpan: ${_formatMS(totalSpan)})';
+    return '$runtimeType(buildDuration: ${_formatMS(buildDuration)}, rasterDuration: ${_formatMS(rasterDuration)}, vsyncOverhead: ${_formatMS(vsyncOverhead)}, totalSpan: ${_formatMS(totalSpan)}, frameNumber: ${_timestamps.last}))';
   }
 }
 

lib/web_ui/lib/src/ui/platform_dispatcher.dart

@@ -204,18 +204,20 @@ class FrameTiming {
     required int buildFinish,
     required int rasterStart,
     required int rasterFinish,
+    int frameNumber = 1,
   }) {
     return FrameTiming._(<int>[
       vsyncStart,
       buildStart,
       buildFinish,
       rasterStart,
-      rasterFinish
+      rasterFinish,
+      frameNumber,
     ]);
   }
 
   FrameTiming._(this._timestamps)
-      : assert(_timestamps.length == FramePhase.values.length);
+      : assert(_timestamps.length == FramePhase.values.length + 1);
 
   int timestampInMicroseconds(FramePhase phase) => _timestamps[phase.index];
 
@@ -232,6 +234,8 @@ class FrameTiming {
   Duration get totalSpan =>
       _rawDuration(FramePhase.rasterFinish) - _rawDuration(FramePhase.vsyncStart);
 
+  int get frameNumber => _timestamps.last;
+
   final List<int> _timestamps; // in microseconds
 
   String _formatMS(Duration duration) => '${duration.inMicroseconds * 0.001}ms';

shell/common/shell.cc

@@ -1353,8 +1353,8 @@ void Shell::ReportTimings() {
 size_t Shell::UnreportedFramesCount() const {
   // Check that this is running on the raster thread to avoid race conditions.
   FML_DCHECK(task_runners_.GetRasterTaskRunner()->RunsTasksOnCurrentThread());
-  FML_DCHECK(unreported_timings_.size() % FrameTiming::kCount == 0);
-  return unreported_timings_.size() / FrameTiming::kCount;
+  FML_DCHECK(unreported_timings_.size() % (FrameTiming::kCount + 1) == 0);
+  return unreported_timings_.size() / (FrameTiming::kCount + 1);
 }
 
 void Shell::OnFrameRasterized(const FrameTiming& timing) {
@@ -1375,6 +1375,7 @@ void Shell::OnFrameRasterized(const FrameTiming& timing) {
     unreported_timings_.push_back(
         timing.Get(phase).ToEpochDelta().ToMicroseconds());
   }
+  unreported_timings_.push_back(timing.GetFrameNumber());
 
   // In tests using iPhone 6S with profile mode, sending a batch of 1 frame or a
   // batch of 100 frames have roughly the same cost of less than 0.1ms. Sending