This change makes Flutter web render tabs as a single space. Previously, tabs rendered differently depending on your platform:

• Windows, Web - a tofu is rendered
• iOS, Android, macOS, Linux - a single space is rendered

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: 'Flutter Demo',
      home: Text('\tHello\tworld\t'),
    );
  }
}

Here was the tab tofu fix for Windows: #34389

Part of flutter/flutter#79153.

Background

Most fonts don't have a glyph for \t, so the "unknown" glyph should be selected and a tofu should be drawn. However, some platforms will override this using their own platform-specific logic and select the glyph for a single space instead. For more information, see: https://bugs.chromium.org/p/skia/issues/detail?id=12334

Skia added a feature to substitute tabs with a single space so that platforms could behave consistently. This feature was added to CanvasKit in version 0.37.0 (skia#574296). This change enables this new feature on Flutter web, thereby making tabs no longer render as a tofu.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide and the C++, Objective-C, Java style guides.
• I listed at least one issue that this PR fixes in the description above.
• I added new tests to check the change I am making or feature I am adding, or Hixie said the PR is test-exempt. See testing the engine for instructions on
  writing and running engine tests.
• I updated/added relevant documentation (doc comments with ///).
• I signed the CLA.
• All existing and new tests are passing.

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