Repository: flutter
Issue: On Android with iOS scrolling behavior, scrolling fast throws IOSScrollViewFlingVelocityTracker.addPosition exception, The position being added (Offset(xx)) has a smaller timestamp than its predecessor: _PointAtTime(Offset(xx) at _
Labels: platform-android,framework,f: gestures,customer: money (g3),P2,team-android,triaged-android

Internal: b/317830530


When theme data of platform is set to `TargetPlatform.iOS` to gain iOS UI behavior,

Scrollable widgets will throw error, when you move it fast and randomly on Android.

## Steps to Reproduce

```dart

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        /// this is the cause of this error !
        /// when removed, everything works jut find !
        platform: TargetPlatform.iOS,
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        appBar: AppBar(
          title: Text('Scroll Test'),
        ),
        body: ListView.builder(
          itemBuilder: (_, i) {
            return Container(
              color: i.isOdd ? Colors.red : Colors.black,
              height: 200,
            );
          },
        ),
      ),
    );
  }
}

```

**Expected results:** 

no errors thrown

**Actual results:** 

When you scroll fast and randomly,

an error will throw

```dart
======== Exception caught by gesture library =======================================================
The following assertion was thrown while routing a pointer event:
The position being added (Offset(225.0, 528.0)) has a smaller timestamp (131:17:15.075000)than its predecessor: _PointAtTime(Offset(225.7, 529.7) at 131:17:15.079000).

When the exception was thrown, this was the stack: 
#0      IOSScrollViewFlingVelocityTracker.addPosition.<anonymous closure> (package:flutter/src/gestures/velocity_tracker.dart:305:7)
#1      IOSScrollViewFlingVelocityTracker.addPosition (package:flutter/src/gestures/velocity_tracker.dart:309:6)
#2      DragGestureRecognizer.handleEvent (package:flutter/src/gestures/monodrag.dart:280:15)
#3      PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:93:12)
#4      PointerRouter._dispatchEventToRoutes.<anonymous closure> (package:flutter/src/gestures/pointer_router.dart:138:9)
...
====================================================================================================
``` 

```
[√] Flutter (Channel stable, 2.0.2, on Microsoft Windows [Version 10.0.19042.868], locale zh-CN)
    • Flutter version 2.0.2 at D:\sdk\flutter
    • Framework revision 8962f6dc68 (8 days ago), 2021-03-11 13:22:20 -0800
    • Engine revision 5d8bf811b3
    • Dart version 2.12.1

[√] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
    • Android SDK at C:\Users\11982\AppData\Local\Android\sdk
    • Platform android-30, build-tools 30.0.2
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)
    • All Android licenses accepted.

[√] Chrome - develop for the web
    • Chrome at C:\Program Files\Google\Chrome\Application\chrome.exe

[√] Android Studio (version 4.1.0)
    • Android Studio at C:\Program Files\Android\Android Studio
    • Flutter plugin can be installed from:
       https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
       https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)

[√] IntelliJ IDEA Ultimate Edition (version 2020.3)
    • IntelliJ at C:\Program Files\JetBrains\IntelliJ IDEA 2020.3.2
    • Flutter plugin version 53.1.5
    • Dart plugin version 203.7759

[√] VS Code (version 1.54.3)
    • VS Code at C:\Users\11982\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension version 3.20.0

[√] Connected device (3 available)
    • YAL AL00 (mobile) • STSDU19527006220 • android-arm64  • Android 10 (API 29)
    • Chrome (web)      • chrome           • web-javascript • Google Chrome 89.0.4389.90
    • Edge (web)        • edge             • web-javascript • Microsoft Edge 89.0.774.54

• No issues found!
```