[flutter] use engine provided frame number (#82934)

packages/flutter/lib/src/scheduler/binding.dart

@@ -202,12 +202,8 @@ mixin SchedulerBinding on BindingBase {
     _instance = this;
 
     if (!kReleaseMode) {
-      int frameNumber = 0;
       addTimingsCallback((List<FrameTiming> timings) {
-        for (final FrameTiming frameTiming in timings) {
-          frameNumber += 1;
-          _profileFramePostEvent(frameNumber, frameTiming);
-        }
+        timings.forEach(_profileFramePostEvent);
       });
     }
   }
@@ -1103,9 +1099,9 @@ mixin SchedulerBinding on BindingBase {
     }
   }
 
-  void _profileFramePostEvent(int frameNumber, FrameTiming frameTiming) {
+  void _profileFramePostEvent(FrameTiming frameTiming) {
     postEvent('Flutter.Frame', <String, dynamic>{
-      'number': frameNumber,
+      'number': frameTiming.frameNumber,
       'startTime': frameTiming.timestampInMicroseconds(FramePhase.buildStart),
       'elapsed': frameTiming.totalSpan.inMicroseconds,
       'build': frameTiming.buildDuration.inMicroseconds,

packages/flutter/test/scheduler/scheduler_test.dart

@@ -143,13 +143,14 @@ void main() {
       buildFinish: 15000,
       rasterStart: 16000,
       rasterFinish: 20000,
+      frameNumber: 1991
     )]);
 
     final List<Map<String, dynamic>> events = scheduler.getEventsDispatched('Flutter.Frame');
     expect(events, hasLength(1));
 
     final Map<String, dynamic> event = events.first;
-    expect(event['number'], isNonNegative);
+    expect(event['number'], 1991);
     expect(event['startTime'], 10000);
     expect(event['elapsed'], 15000);
     expect(event['build'], 5000);