[cupertino_ui] Fix covered sheet revealing root route through top gap - #12530

…er#191734)

flutter/packages@df2ba94...740f093

2026-08-25 srawlins@google.com [cupertino_ui] Remove unused parameters
from constructors of generic classes. (flutter/packages#12457)
2026-08-25 srawlins@google.com [material_ui] Remove unused parameters
from constructors of generic classes. (flutter/packages#12458)
2026-08-25 6655696+guidezpl@users.noreply.github.com Ignore shared code
for iOS platform implementation of Google Maps plugin
(flutter/packages#12529)
2026-08-25 136096126+glitchfl@users.noreply.github.com [cross_file]
fixed `readAsString` decoding in-memory bytes as UTF-16
(flutter/packages#12479)
2026-08-25 lozhkovoi@gmail.com [cupertino_ui] Remove two items assert to
allow CupertinoTabBar to have one tab (flutter/packages#12546)
2026-08-25 huahua8893@sina.cn [cupertino_ui] Fix covered sheet revealing
root route through top gap (flutter/packages#12530)
2026-08-25 fluttergithubbot@gmail.com Sync release-go_router-18.0.0 to
main (flutter/packages#12575)
2026-08-25 fluttergithubbot@gmail.com Sync release-material_ui-1.1.0 to
main (flutter/packages#12577)
2026-08-25 fluttergithubbot@gmail.com Sync release-cupertino_ui-1.0.1 to
main (flutter/packages#12576)
2026-08-24 41930132+hellohuanlin@users.noreply.github.com
[quick_actions_ios]unskip XCUITests (flutter/packages#12436)
2026-08-24 karthimanikuttan001@gmail.com Fix RangeSlider thumb overlay
remains visible after touch interaction ends (flutter/packages#12560)
2026-08-24 victor.orozco@cloudsufi.com [google_sign_in] Increase iOS
coverage tests (flutter/packages#12484)
2026-08-24 269567208+reidbaker-agent@users.noreply.github.com
[camera_android_camerax] Migrate from dart_skills_lint to skills_lint
(flutter/packages#12543)
2026-08-24 74037732+developerashkan@users.noreply.github.com [go_router]
Clarify onEnter/redirect ordering, add regression test
(flutter/packages#12337)
2026-08-24 brunocorona.alcantar@gmail.com [material_ui] Port
flutter/flutter flutter#185149 "Slider label clips the screen"
(flutter/packages#12572)
2026-08-24 engine-flutter-autoroll@skia.org Roll Flutter from
65c9a8d to 9a82789 (17 revisions) (flutter/packages#12578)
2026-08-24 stuartmorgan@google.com [tool] Fix dart_test.yaml parsing
(flutter/packages#12574)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-packages-flutter-autoroll
Please CC flutter-ecosystem@google.com on the revert to ensure that a
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…flutter#12530)

Ports flutter/flutter#187058 to `cupertino_ui` following flutter/flutter#188444.

Fixes flutter/flutter#187057.

When multiple `CupertinoSheetRoute`s are stacked, the covered sheet's top gap can reveal the root route because the top-gap padding sits outside the secondary route transition.

This change applies the covered sheet's secondary transition outside the top-gap padding, so the sheet and its gap move together. It also adds a coordinate-based regression test that verifies the root route remains fully covered.

## Tests

- `flutter test test/sheet_test.dart --no-pub`
- `dart run script/tool/bin/flutter_plugin_tools.dart analyze --packages cupertino_ui`
- `dart run script/tool/bin/flutter_plugin_tools.dart validate --packages cupertino_ui --base-sha=252bb33ad3666c7d28621c87edccafff86e210fd --check-for-missing-changes`
- `dart run script/tool/bin/flutter_plugin_tools.dart publish-check --packages cupertino_ui`

## Pre-Review Checklist

…flutter#12530)

Ports flutter/flutter#187058 to `cupertino_ui` following flutter/flutter#188444.

Fixes flutter/flutter#187057.

When multiple `CupertinoSheetRoute`s are stacked, the covered sheet's top gap can reveal the root route because the top-gap padding sits outside the secondary route transition.

This change applies the covered sheet's secondary transition outside the top-gap padding, so the sheet and its gap move together. It also adds a coordinate-based regression test that verifies the root route remains fully covered.

## Tests

- `flutter test test/sheet_test.dart --no-pub`
- `dart run script/tool/bin/flutter_plugin_tools.dart analyze --packages cupertino_ui`
- `dart run script/tool/bin/flutter_plugin_tools.dart validate --packages cupertino_ui --base-sha=252bb33ad3666c7d28621c87edccafff86e210fd --check-for-missing-changes`
- `dart run script/tool/bin/flutter_plugin_tools.dart publish-check --packages cupertino_ui`

## Pre-Review Checklist