[ashu3699]

Ports the Material-side test change of flutter/flutter#195288, following the porting instructions in flutter/flutter#188444 (Material is frozen in flutter/flutter; its tests now live here).

What this PR changes

The DataTable cell has correct semantics rect regression test (flutter/flutter#171264) asserted the internal transform distribution of the table's synthesized semantics nodes: that the labeled cell node carries transform = null with an origin-based rect. That shape is an implementation detail — the same assistive-technology-visible box can be produced with the transform living on the cell's own node instead of on a synthesized ancestor.

The assertion now composes the transform chain from the root of the semantics tree and checks the laid-out cell box (0, 56) → (302, 126) directly. That holds regardless of how the table distributes transforms between its synthesized row/cell nodes and the cell's own node, while still catching the #171264 bug class (a wrong cell box).

Verified against both the current Flutter framework and the pending framework change in flutter/flutter#195288: the test passes on either, so this PR can land independently of that one.

Issues fixed

• Ports the test/material side of Fix table cell semantics offsets across assemble passes flutter#195288 (per the freeze-porting process in [Decoupling] Port over open PRs from flutter/flutter to material_ui or cupertino_ui flutter#188444).
• Keeps the regression coverage for Semantics is misaligned with actual component on web flutter#171264 in its new home.

Pre-Review Checklist

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• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I followed the version and CHANGELOG instructions, using semantic versioning and the repository CHANGELOG style, or I have commented below to indicate which documented exception this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

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Footnotes

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[gemini-code-assist]

Code Review

This pull request updates the DataTable cell semantics regression test to assert the cell's composed rect from the root of the semantics tree, introducing a helper method _semanticsWorldRect to traverse the semantics tree. The review feedback suggests adding explicit checks and descriptive error messages in this helper method to handle cases where semantics are not enabled or the target node is not found, preventing generic null check errors.