Repository: flutter
Issue: Low performance while scrolling over a large list of emojis
Labels: framework,c: performance,f: scrolling,perf: speed,has reproducible steps,P2,found in release: 2.5,found in release: 2.6,team-framework,triaged-framework

## Details

I'm having some jank frames randomly while scrolling very fast over a large list of different emojis.

The emojis are displayed in a Text widget each, and arranged as Rows in a ListView widget, which is in turn surrounded between a TextField in the top and a TabBar at the bottom. All of this is inside a DraggableScrollableSheet.

https://gist.github.com/jdosornio/63ea7a28774a8fa2a85a382f1c8d9a2c



https://user-images.githubusercontent.com/11827332/140101737-3364ebcb-0462-4af3-9187-a091d41de141.MP4

[dart_devtools_2021_11_3-1635954929370000.json.zip](https://github.com/flutter/flutter/files/7469239/dart_devtools_2021_11_3-1635954929370000.json.zip)


**Target Platform:**
iOS
**Target OS version/browser:**
14.4.2
**Devices:**
iPhone X

```
flutter analyze 
Analyzing emoji_performance...                                          
No issues found! (ran in 2.2s)
```


```
flutter doctor -v
[✓] Flutter (Channel master, 2.6.0-12.0.pre.566, on macOS 11.5.2 20G95 darwin-x64, locale fr-US)
    • Flutter version 2.6.0-12.0.pre.566 at ~/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 607d7934c7 (13 hours ago), 2021-11-02 21:23:01 -0700
    • Engine revision 6095a13678
    • Dart version 2.15.0 (build 2.15.0-268.0.dev)

[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.0)
    • Android SDK at ~/Library/Android/sdk
    • Platform android-30, build-tools 30.0.0
    • Java binary at: /Applications/Android Studio.app/Contents/jre/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 11.0.10+0-b96-7281165)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 13.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • CocoaPods version 1.10.1

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2020.3)
    • 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 11.0.10+0-b96-7281165)

[✓] VS Code (version 1.61.2)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension can be installed from:
      🔨 https://marketplace.visualstudio.com/items?itemName=Dart-Code.flutter

[✓] VS Code (version 1.36.1)
    • VS Code at ~/Downloads/Visual Studio Code.app/Contents
    • Flutter extension can be installed from:
      🔨 https://marketplace.visualstudio.com/items?itemName=Dart-Code.flutter

[✓] Connected device (3 available)
    • iPhone de Donaldo (mobile) • efc0fce738015e17e44afdbf05897412814775d2 • ios            • iOS 14.4.2 18D70
    • macOS (desktop)            • macos                                    • darwin-x64     • macOS 11.5.2 20G95 darwin-x64
    • Chrome (web)               • chrome                                   • web-javascript • Google Chrome 95.0.4638.69

• No issues found!
```