[web] Apply autocapitalize to text editing elements

[flutter-zl]

Fixes #187231

Problem

Flutter web does not apply TextCapitalization to the hidden .flt-text-editing input for all text editing strategies. On Chromebook OSK, this can cause the first typed letter to be capitalized even when the app uses TextCapitalization.none.

Fix

Apply autocapitalize in the shared DefaultTextEditingStrategy.applyConfiguration path so all web strategies write the correct DOM attribute.

Demo

Before	After
https://flutter-demo-43-before.web.app	https://flutter-demo-43-after.web.app

Steps: enable Chromebook on-screen keyboard, focus the Flutter text field, dismiss the keyboard, refocus the field, then type a.

Before: the hidden Flutter input is missing autocapitalize, and Chromebook OSK may type A.
After: the hidden Flutter input has autocapitalize="off", and Chromebook OSK types a.

Manual validation

• Confirmed before DOM omitted autocapitalize on .flt-text-editing.
• Confirmed after DOM includes autocapitalize="off" on .flt-text-editing.
• Confirmed Chromebook OSK behavior works as expected on the after demo.

[gemini-code-assist]

Code Review

This pull request refactors how onscreen canvases are styled as overlays by dynamically setting the position: absolute CSS property only when platform views are present, rather than hardcoding it. It also centralizes the application of the autocapitalize attribute in text editing strategies and updates corresponding tests. The review feedback suggests wrapping a test's JS configuration override in a try-finally block to prevent test pollution and correcting a misleading copy-pasted comment in the text editing tests.

I am having trouble creating individual review comments. Click here to see my feedback.

engine/src/flutter/lib/web_ui/test/ui/platform_view_position_test.dart (25-64)

To prevent test pollution, wrap the test body in a try-finally block to ensure that engine.debugOverrideJsConfiguration(null) is always executed, even if the test fails or throws an exception. This ensures subsequent tests are not affected by a leftover global JS configuration override.

  test('base onscreen canvas is not positioned as an overlay', () async {
    if (!isCanvasKit) {
      return;
    }

    // Force multi-surface mode to ensure OnscreenCanvasProvider is used.
    engine.debugOverrideJsConfiguration(
      <String, Object?>{'canvasKitForceMultiSurfaceRasterizer': true}.jsify()
          as engine.JsFlutterConfiguration?,
    );
    try {
      // Reset the renderer to ensure it is created with the new configuration.
      engine.renderer.debugResetRasterizer();
      engine.renderer.debugClear();

      // Create a scene with only Flutter content. This uses the base canvas, not
      // an overlay canvas interleaved with platform views.
      final recorder = ui.PictureRecorder();
      final canvas = ui.Canvas(recorder);
      canvas.drawRect(
        const ui.Rect.fromLTWH(0, 0, 100, 100),
        ui.Paint()..color = const ui.Color(0xFFFF0000),
      );

      final sb = ui.SceneBuilder();
      sb.addPicture(ui.Offset.zero, recorder.endRecording());

      await renderScene(sb.build());

      final DomElement canvasElement = (implicitView as engine.EngineFlutterView).dom.sceneHost
          .querySelectorAll('canvas')
          .single;

      expect(
        canvasElement.style.position,
        isNot('absolute'),
        reason: 'Base canvas should not be styled as a platform-view overlay.',
      );
    } finally {
      engine.debugOverrideJsConfiguration(null);
    }
  });

References

1. Code should be tested and follow the guidance described in the writing effective tests guide. ^(link)

engine/src/flutter/lib/web_ui/test/engine/text_editing_test.dart (1931)

The comment mentions creating a configuration with an AutofillGroup of four text fields, but the code actually creates a single text field configuration with sentences capitalization. This appears to be a copy-paste comment error and should be corrected to avoid confusion.

      // Create a configuration with sentences capitalization.

References

1. Optimize for readability: Code is read more often than it is written. ^(link)

[harryterkelsen]

LGTM

[auto-submit]

autosubmit label was removed for flutter/flutter/188351, because The base commit of the PR is older than 7 days and can not be merged. Please merge the latest changes from the main into this branch and resubmit the PR.