title: Flutter Web: Cannot scroll with mouse down (drag) (Flutter 2.5+)
body: <h2>[Update]</h2>
  <p>I can confirm this issue happened in flutter above 2.5. Using 2.2.3 is fine. The question becomes why this feature been removed in 2.5 ? And how to enable it in flutter 2.5?</p>
  <h2>[Origin Question]</h2>
  <p>I'm using SingleChildScrollView on flutter web with desktop browser. Scrolling only works on mouse wheel but not on mouse click (drag). How can I map mouse click to touch and scroll like mobile?</p>
  <pre class="lang-dart prettyprint-override"><code>import 'package:flutter/material.dart';
  
  void main() {
    runApp(const MyApp());
  }
  
  class MyApp extends StatelessWidget {
    const MyApp({Key? key}) : super(key: key);
    @override
    Widget build(BuildContext context) {
      return MaterialApp(
        title: 'Flutter Demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: SingleChildScrollView(
          child: Column(
            children: List&lt;Widget&gt;.generate(50, (i) =&gt; Text(i.toString())).toList(),
          ),
        ),
      );
    }
  }
  </code></pre>
  <pre><code>flutter doctor -v
  [✓] Flutter (Channel master, 2.6.0-6.0.pre.6, on Ubuntu 20.04.3 LTS 5.11.0-34-generic, locale en_US.UTF-8)
      • Flutter version 2.6.0-6.0.pre.6 at /home/XXX
      • Upstream repository https://github.com/flutter/flutter.git
      • Framework revision 0c5431d99c (12 days ago), 2021-09-05 22:31:02 -0400
      • Engine revision b9c633900e
      • Dart version 2.15.0 (build 2.15.0-82.0.dev)
  
  [✓] Chrome - develop for the web
      • Chrome at google-chrome
  
  [✓] Connected device (2 available)
      • Linux (desktop) • linux  • linux-x64      • Ubuntu 20.04.3 LTS 5.11.0-34-generic
      • Chrome (web)    • chrome • web-javascript • Google Chrome 93.0.4577.82
  </code></pre>