Roll engine 85492c3e804a..4812a2af115c (3 commits) (#27518)

https://github.com/flutter/engine/compare/85492c3e804a...4812a2af115c

git log 85492c3e804a6f6bf06275ed49c103ac6548be87..4812a2af115ce81c0ad1dec8680fdf9ea7dd4fc4 --no-merges --oneline
4812a2af1 DCHECK that clip layer's behavior isn't none (flutter/engine#7659)
eaae8a67b Retained rendering in Fuchsia PhysicalShapeLayer (flutter/engine#6558)
194608290 Move Brightness definition to dart:ui (#27479) (flutter/engine#7678)

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bin/internal/engine.version

-85492c3e804a6f6bf06275ed49c103ac6548be87
+4812a2af115ce81c0ad1dec8680fdf9ea7dd4fc4