[Android] Fix scrolling performance in shadowed containers

[kubaflo]

Note

Are you waiting for the changes in this PR to be merged?
It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!

Root Cause

#35623 made PlatformWrapperView.onDescendantInvalidated() call invalidate() for every descendant update whenever the wrapper had a shadow. That keeps an immediate child animation such as a shadowed Switch in sync, but it also makes scrolling descendants redraw the entire shadowed container for every item update.

The complete reproduction from MrLazyLee/ScrollPerformance has two large shadow wrappers around the CollectionView:

• The CommunityToolkit popup's default shadow.
• An explicit shadow on the inner Border.

Instrumentation over four up/down scroll cycles recorded:

Wrapper	Descendant invalidations	Immediate-child invalidations
Popup, 1079 x 1678	1,859	3
Border, 1026 x 1306	1,803	2

The current code therefore forces thousands of full-popup redraws even though only five invalidations originate from the immediate children whose shadows may need to move.

Description of Change

Only invalidate a shadow wrapper when Android reports that the invalidation target is its immediate child (child == target). Deeper descendants continue to redraw through their own RenderNodes without forcing the whole shadowed ancestor to re-record its display list.

This preserves the #35623 behavior for controls such as Switch, while removing the scrolling regression for nested CollectionView and ScrollView content.

Verification

The author reproduction was built with the exact 10.0.90 source and the same locally-built native AAR for both control and patched runs. Each row below used the same emulator and automated eight-cycle scroll sequence without screen recording:

Variant	50th percentile	90th percentile	Slow UI-thread frames
10.0.80	34 ms	53 ms	29
10.0.90 control	42-44 ms	53-61 ms	106-118
10.0.90 with this fix	34-38 ms	57-61 ms	28-47

The patched result returns to the 10.0.80 range. The Android Core View device-test category also passes: 76 run, 74 passed, 2 ignored, 0 failed. A focused test verifies that an immediate child still invalidates a shadow while a deeper descendant does not.

Videos

10.0.80 baseline

ScrollPerformance-10.0.80-evidence.mp4

10.0.90 regression

ScrollPerformance-10.0.90-regression.mp4

10.0.90 with this fix

ScrollPerformance-10.0.90-fixed.mp4

Issues Fixed

Fixes #37281

Regressed by #35623.

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[sheiksyedm]

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[kubaflo]

/backport to main

[kubaflo]

/backport to release/10.0.1xx-sr10

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Started backporting to main (link to workflow run)

[github-actions]

Started backporting to release/10.0.1xx-sr10 (link to workflow run)