Fix semantics and transition-perf tests to parse new event format. (#47899)

dev/benchmarks/complex_layout/test_driver/semantics_perf_test.dart

@@ -34,9 +34,9 @@ void main() {
       });
 
       final Iterable<TimelineEvent> semanticsEvents = timeline.events.where((TimelineEvent event) => event.name == 'Semantics');
-      if (semanticsEvents.length != 1)
-        fail('Expected exactly one semantics event, got ${semanticsEvents.length}');
-      final Duration semanticsTreeCreation = semanticsEvents.first.duration;
+      if (semanticsEvents.length != 2)
+        fail('Expected exactly two semantics events, got ${semanticsEvents.length}');
+      final Duration semanticsTreeCreation = Duration(microseconds: semanticsEvents.last.timestampMicros - semanticsEvents.first.timestampMicros);
 
       final String jsonEncoded = json.encode(<String, dynamic>{'initialSemanticsTreeCreation': semanticsTreeCreation.inMilliseconds});
       File(p.join(testOutputsDirectory, 'complex_layout_semantics_perf.json')).writeAsStringSync(jsonEncoded);

examples/flutter_gallery/test_driver/transitions_perf_test.dart

@@ -66,6 +66,7 @@ List<String> _allDemos = <String>[];
 Future<void> saveDurationsHistogram(List<Map<String, dynamic>> events, String outputPath) async {
   final Map<String, List<int>> durations = <String, List<int>>{};
   Map<String, dynamic> startEvent;
+  int frameStart;
 
   // Save the duration of the first frame after each 'Start Transition' event.
   for (Map<String, dynamic> event in events) {
@@ -74,10 +75,19 @@ Future<void> saveDurationsHistogram(List<Map<String, dynamic>> events, String ou
       assert(startEvent == null);
       startEvent = event;
     } else if (startEvent != null && eventName == 'Frame') {
-      final String routeName = startEvent['args']['to'] as String;
-      durations[routeName] ??= <int>[];
-      durations[routeName].add(event['dur'] as int);
-      startEvent = null;
+      final String phase = event['ph'] as String;
+      final int timestamp = event['ts'] as int;
+      if (phase == 'B') {
+        assert(frameStart == null);
+        frameStart = timestamp;
+      } else {
+        assert(phase == 'E');
+        final String routeName = startEvent['args']['to'] as String;
+        durations[routeName] ??= <int>[];
+        durations[routeName].add(timestamp - frameStart);
+        startEvent = null;
+        frameStart = null;
+      }
     }
   }