[cupertino_ui] Fix platform view sheet transitions - #12565

From flutter/flutter#182935
Fixes flutter/flutter#169495

The scale transition in showCupertinoSheet for the underlying route defaulted to FilterQuality.medium, which pushes an implicit `ImageFilterLayer`.

Platform views cannot be correctly sampled or transformed by rasterization-based filters. Consequently, they fail to reflect the scale transformation during the transition animation when an `ImageFilterLayer` is present, leading to a broken visual effect where the background scales but the platform view remains at its original size.

**Solution:**
Added `hasPlatformView` parameter. `false` by default which matches the original behavior. When set to `true`, we use standard `TransformLayer` by setting filterQuality to `null`.

## Pre-Review Checklist

flutter/packages@36e088a...8a35b16

2026-09-10 [email protected] [material_ui]
Migrate M3 buttons template to use new gen_defaults
(flutter/packages#12744)
2026-09-09 [email protected] [cupertino_ui]Add awaitNotRequired to
Future-returning callsites without await (flutter/packages#12817)
2026-09-09 [email protected] [material_ui] Add awaitNotRequired
annotation to material_ui (flutter/packages#12622)
2026-09-09 [email protected] [image_picker] Add native tests
for photo-library access and UIImagePicker completion
(flutter/packages#12540)
2026-09-09 [email protected] [material_ui][cupertino_ui] allow page
routes to opt out of route semantics - flutter#182556 (flutter/packages#12674)
2026-09-09 [email protected] [image_picker] Add native tests
for pick results, camera access, and presentation
(flutter/packages#12539)
2026-09-09 [email protected] [cupertino_ui] Fix platform view sheet
transitions (flutter/packages#12565)
2026-09-09 [email protected]
[camera_android_camerax] Bump cameraxVersion to 1.6.2, remove
concurrent-futures workaround (flutter/packages#12698)
2026-09-09 [email protected] `[material_ui]`
replace identical checks with equality when dealing with enums
(flutter/packages#12633)
2026-09-09 [email protected] Roll Flutter from
b444e78 to 63b9518 (21 revisions) (flutter/packages#12814)
2026-09-09 [email protected]
`[cupertino_ui]` replace identical checks with equality when dealing
with enums (flutter/packages#12632)
2026-09-09 [email protected] [pigeon] add support for multiple swift
outputs (flutter/packages#12720)

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… stays and the AI chat shows (#166)

TestFlight 55 (Roman, 30 Oct): the AI chat opened over an article showed
only the top of its header and its composer. Flutter's sheet shrinks the
screen under it, and a sheet under a new sheet, with ScaleTransition and
FilterQuality.medium, an image filter iOS's views cannot follow
(flutter/flutter#169495). Since #166 the article's glass and the chat's
close button stay iOS's under a sheet, so the filter met them.

Every sheet now opens through showSheet (core/sheet.dart): Flutter's
CupertinoSheetRoute, with the screen under it moved by a copy of Flutter's
own delegated transition without the filter, and a covered sheet moved by
the same transform from outside Flutter's transition. This is Flutter's own
fix (hasPlatformView in cupertino_ui, flutter/packages#12565), which our
SDK does not have. The glass stays iOS's; no Flutter stand-in comes back.

Tests: no image filter under the app's sheet, the screen and a covered
sheet in the same place and size as under Flutter's, the glass still iOS's,
showSheet's result, and no showCupertinoSheet left in the app.

Co-Authored-By: Claude Opus 5.5 <[email protected]>