Revert engine back to afb9d510c3bb0f1b97980434b41200a2d3491697 (#33982)

Revert "Add currentSystemFrameTimeStamp to SchedulerBinding (#33886)"

This reverts commit 61b83d32.

bin/internal/engine.version

-3371da1e09511cb047c746e8209ec91550714b05
+afb9d510c3bb0f1b97980434b41200a2d3491697

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

@@ -846,22 +846,6 @@ mixin SchedulerBinding on BindingBase, ServicesBinding {
   }
   Duration _currentFrameTimeStamp;
 
-  /// The raw time stamp as provided by the engine to [Window.onBeginFrame]
-  /// for the frame currently being processed.
-  ///
-  /// Unlike [currentFrameTimeStamp], this time stamp is neither adjusted to
-  /// offset when the epoch started nor scaled to reflect the [timeDilation] in
-  /// the current epoch.
-  ///
-  /// On most platforms, this is a more or less arbitrary value, and should
-  /// generally be ignored. On Fuchsia, this corresponds to the system-provided
-  /// presentation time, and can be used to ensure that animations running in
-  /// different processes are synchronized.
-  Duration get currentSystemFrameTimeStamp {
-    assert(_lastRawTimeStamp != null);
-    return _lastRawTimeStamp;
-  }
-
   int _profileFrameNumber = 0;
   final Stopwatch _profileFrameStopwatch = Stopwatch();
   String _debugBanner;

packages/flutter/test/scheduler/scheduler_test.dart

@@ -8,7 +8,6 @@ import 'package:flutter/scheduler.dart';
 import 'package:flutter/services.dart';
 
 import '../flutter_test_alternative.dart';
-import 'scheduler_tester.dart';
 
 class TestSchedulerBinding extends BindingBase with ServicesBinding, SchedulerBinding { }
 
@@ -136,36 +135,4 @@ void main() {
     expect(scheduler.schedulerPhase, SchedulerPhase.idle);
     expect(taskExecuted, false);
   });
-
-  test('currentSystemFrameTimeStamp is the raw timestamp', () {
-    Duration lastTimeStamp;
-    Duration lastSystemTimeStamp;
-
-    void frameCallback(Duration timeStamp) {
-      expect(timeStamp, scheduler.currentFrameTimeStamp);
-      lastTimeStamp = scheduler.currentFrameTimeStamp;
-      lastSystemTimeStamp = scheduler.currentSystemFrameTimeStamp;
-    }
-
-    scheduler.scheduleFrameCallback(frameCallback);
-    tick(const Duration(seconds: 2));
-    expect(lastTimeStamp, Duration.zero);
-    expect(lastSystemTimeStamp, const Duration(seconds: 2));
-
-    scheduler.scheduleFrameCallback(frameCallback);
-    tick(const Duration(seconds: 4));
-    expect(lastTimeStamp, const Duration(seconds: 2));
-    expect(lastSystemTimeStamp, const Duration(seconds: 4));
-
-    timeDilation = 2;
-    scheduler.scheduleFrameCallback(frameCallback);
-    tick(const Duration(seconds: 6));
-    expect(lastTimeStamp, const Duration(seconds: 2)); // timeDilation calls SchedulerBinding.resetEpoch
-    expect(lastSystemTimeStamp, const Duration(seconds: 6));
-
-    scheduler.scheduleFrameCallback(frameCallback);
-    tick(const Duration(seconds: 8));
-    expect(lastTimeStamp, const Duration(seconds: 3)); // 2s + (8 - 6)s / 2
-    expect(lastSystemTimeStamp, const Duration(seconds: 8));
-  });
 }