Video does not work with ShaderMask

### Steps to reproduce

Checkout https://github.com/willsmanley/video_shader

### Expected results

Video should be masked to only be visible through the text, just like in the working image shader example.

Here is a working example in JS of using a video as a text background: https://video-background-b9b.pages.dev/

The flutter widget of the week video from 2020 actually shows a video mask working with flames at the very end, but does not provide source code for it: https://www.youtube.com/watch?v=7sUL66pTQ7Q

### Actual results

Video overflows the text and is not masked.

### Code sample

https://github.com/willsmanley/video_shader

### Screenshots or Video

_No response_

### Logs

_No response_

### Flutter Doctor output

[✓] Flutter (Channel stable, 3.24.4, on macOS 15.1 24B83 darwin-arm64, locale en-US)
• Flutter version 3.24.4 on channel stable at /Users/admin/flutter/flutter
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision 603104015d (2 months ago), 2024-10-24 08:01:25 -0700
• Engine revision db49896cf2
• Dart version 3.5.4
• DevTools version 2.37.3

[✗] Android toolchain - develop for Android devices
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(or visit https://flutter.dev/to/macos-android-setup for detailed instructions).
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[✓] Xcode - develop for iOS and macOS (Xcode 16.1)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Build 16B40
• CocoaPods version 1.16.2

[✓] Chrome - develop for the web
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[!] Android Studio (not installed)
• Android Studio not found; download from https://developer.android.com/studio/index.html
(or visit https://flutter.dev/to/macos-android-setup for detailed instructions).

[✓] Connected device (3 available)
• macOS (desktop) • macos • darwin-arm64 • macOS 15.1 24B83 darwin-arm64
• Mac Designed for iPad (desktop) • mac-designed-for-ipad • darwin • macOS 15.1 24B83 darwin-arm64
• Chrome (web) • chrome • web-javascript • Google Chrome 131.0.6778.205

[✓] Network resources
• All expected network resources are available.