Repository: flutter
Issue: [web:html] GIF stops playing in scrollable widgets in Mobile Browsers upon scrolling 
Labels: framework,f: scrolling,platform-web,a: images,a: build,e: web_html,has reproducible steps,P2,browser: safari-ios,found in release: 3.0,found in release: 3.1,team-web,triaged-web

**Issue** 
GIF stops playing in scrollable widgets in Mobile Browsers upon scrolling as shown in the video below using both Safari and Chrome in a physical iPhone-11  device. 

https://user-images.githubusercontent.com/46427323/111178369-1f469f80-85bc-11eb-99da-7c0aac05d644.mov


**Expected results:** 
The GIF should keep playing while scrolling similar to Flutter iOS, Android, and Web-Desktop. 


## Steps to Reproduce

1. Using the given code sample below, run `flutter build web --release`.
2. Serve the web content (e.g. `python3 -m http.server --directory build/web 8000`)
3. Open the web app in a physical iPhone browser.
4. Observe the behavior.


## Additional Context
As I looked more into it, I also found out that in all the following cases, the **GIF does not play at all**:
- Safari in Web-Desktop. 
- Safari in the iPhone Simulator _(given in the flutter doctor output)_.
- Using `flutter build web --release --web-renderer=canvaskit` in mobile browser (both Chrome/Safari). 

<details><summary> Minimal Code Sample to Reproduce:</summary>

```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(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatelessWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: Center(
        child: SingleChildScrollView(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Container(height: 300.0, width: 100.0, color: Colors.blue,),
              Image.network('https://media.giphy.com/media/eLvDUFkSRdbwNtRwjf/giphy.gif'),
              Container(height: 300.0, width: 100.0, color: Colors.blue,),
              Image.network('https://media.giphy.com/media/3ov9jIDUH1IHp6nAWs/giphy.gif'),
              Container(height: 300.0, width: 100.0, color: Colors.blue,),
            ],
          ),
        ),
      ),
    );
  }
}
```

</details>



<details>
  <summary>Flutter Doctor</summary>

```
[✓] Flutter (Channel stable, 2.0.2, on Mac OS X 10.15.6 19G2021 darwin-x64, locale en)
    • Flutter version 2.0.2 at /Users/osaxma/fvm/versions/stable
    • Framework revision 8962f6dc68 (4 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 29.0.2)
    • Android SDK at /Users/osaxma/Library/Android/sdk
    • Platform android-30, build-tools 29.0.2
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6915495)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 12.3, Build version 12C33
    • CocoaPods version 1.10.1

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 4.1)
    • Android Studio at /Applications/Android Studio.app/Contents
    • 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-b3-6915495)

[✓] VS Code (version 1.54.2)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.20.0

[✓] Connected device (2 available)
    • iPhone 12 Pro Max (mobile) • 5D894941-88ED-47BA-8FE0-0FA45101E676 • ios            • com.apple.CoreSimulator.SimRuntime.iOS-14-3 (simulator)
    • Chrome (web)               • chrome                               • web-javascript • Google Chrome 89.0.4389.82

• No issues found!
```

</details>