There's a double loop in the overlay computation logic which can be expensive:

https://github.com/flutter/engine/blob/5a12de1beab71c44692e7b12e7fdf3f5f3702f06/shell/platform/darwin/ios/framework/Source/FlutterPlatformViews.mm#L698-L705

For example, some of the intermediate rect structs can be cashed for re-use.

More context: flutter/engine#51687 (comment)

CC @flar

Creating a separate issue since it's the existing behavior. We should keep the original PR atomic, and have a separate PR for this, so that we can measure the improvement.