add rasterizer start times to timeline summaries (#58514)

packages/flutter_driver/lib/src/driver/timeline_summary.dart

@@ -19,6 +19,12 @@ const JsonEncoder _prettyEncoder = JsonEncoder.withIndent('  ');
 /// phase. Anything past that is in the danger of missing the frame as 60FPS.
 const Duration kBuildBudget = Duration(milliseconds: 16);
 
+/// The name of the framework frame build events we need to filter or extract.
+const String kBuildFrameEventName = 'Frame';
+
+/// The name of the engine frame rasterization events we need to filter or extract.
+const String kRasterizeFrameEventName = 'GPURasterizer::Draw';
+
 /// Extracts statistics from a [Timeline].
 class TimelineSummary {
   /// Creates a timeline summary given a full timeline object.
@@ -84,6 +90,9 @@ class TimelineSummary {
   /// The total number of frames recorded in the timeline.
   int countFrames() => _extractFrameDurations().length;
 
+  /// The total number of rasterizer cycles recorded in the timeline.
+  int countRasterizations() => _extractGpuRasterizerDrawDurations().length;
+
   /// Encodes this summary as JSON.
   Map<String, dynamic> get summaryJson {
     final SceneDisplayLagSummarizer sceneDisplayLagSummarizer = _sceneDisplayLagSummarizer();
@@ -100,18 +109,22 @@ class TimelineSummary {
       'worst_frame_rasterizer_time_millis': computeWorstFrameRasterizerTimeMillis(),
       'missed_frame_rasterizer_budget_count': computeMissedFrameRasterizerBudgetCount(),
       'frame_count': countFrames(),
+      'frame_rasterizer_count': countRasterizations(),
       'frame_build_times': _extractFrameDurations()
           .map<int>((Duration duration) => duration.inMicroseconds)
           .toList(),
       'frame_rasterizer_times': _extractGpuRasterizerDrawDurations()
           .map<int>((Duration duration) => duration.inMicroseconds)
           .toList(),
-      'frame_begin_times': _extractBeginTimestamps('Frame')
+      'frame_begin_times': _extractBeginTimestamps(kBuildFrameEventName)
+          .map<int>((Duration duration) => duration.inMicroseconds)
+          .toList(),
+      'frame_rasterizer_begin_times': _extractBeginTimestamps(kRasterizeFrameEventName)
           .map<int>((Duration duration) => duration.inMicroseconds)
           .toList(),
       'average_vsync_transitions_missed': sceneDisplayLagSummarizer.computeAverageVsyncTransitionsMissed(),
       '90th_percentile_vsync_transitions_missed': sceneDisplayLagSummarizer.computePercentileVsyncTransitionsMissed(90.0),
-      '99th_percentile_vsync_transitions_missed': sceneDisplayLagSummarizer.computePercentileVsyncTransitionsMissed(99.0)
+      '99th_percentile_vsync_transitions_missed': sceneDisplayLagSummarizer.computePercentileVsyncTransitionsMissed(99.0),
     };
   }
 
@@ -227,7 +240,7 @@ class TimelineSummary {
 
   SceneDisplayLagSummarizer _sceneDisplayLagSummarizer() => SceneDisplayLagSummarizer(_extractNamedEvents(kSceneDisplayLagEvent));
 
-  List<Duration> _extractGpuRasterizerDrawDurations() => _extractBeginEndEvents('GPURasterizer::Draw');
+  List<Duration> _extractGpuRasterizerDrawDurations() => _extractBeginEndEvents(kRasterizeFrameEventName);
 
-  List<Duration> _extractFrameDurations() => _extractBeginEndEvents('Frame');
+  List<Duration> _extractFrameDurations() => _extractBeginEndEvents(kBuildFrameEventName);
 }

packages/flutter_driver/test/src/real_tests/timeline_summary_test.dart

@@ -372,9 +372,11 @@ void main() {
             'worst_frame_rasterizer_time_millis': 20.0,
             'missed_frame_rasterizer_budget_count': 2,
             'frame_count': 3,
+            'frame_rasterizer_count': 3,
             'frame_build_times': <int>[17000, 9000, 19000],
             'frame_rasterizer_times': <int>[18000, 10000, 20000],
             'frame_begin_times': <int>[0, 18000, 28000],
+            'frame_rasterizer_begin_times': <int>[0, 18000, 28000],
             'average_vsync_transitions_missed': 0.0,
             '90th_percentile_vsync_transitions_missed': 0.0,
             '99th_percentile_vsync_transitions_missed': 0.0
@@ -431,9 +433,11 @@ void main() {
           'worst_frame_rasterizer_time_millis': 20.0,
           'missed_frame_rasterizer_budget_count': 2,
           'frame_count': 3,
+          'frame_rasterizer_count': 3,
           'frame_build_times': <int>[17000, 9000, 19000],
           'frame_rasterizer_times': <int>[18000, 10000, 20000],
           'frame_begin_times': <int>[0, 18000, 28000],
+          'frame_rasterizer_begin_times': <int>[0, 18000, 28000],
           'average_vsync_transitions_missed': 8.0,
           '90th_percentile_vsync_transitions_missed': 12.0,
           '99th_percentile_vsync_transitions_missed': 12.0