Flutter web assumes there is a single accessibility root node with ID 0. In a multi-window world, there may be multiple root nodes each with their own unique ID. Thus, Flutter web must not rely on the root node having ID 0.

See:

1. https://github.com/flutter/engine/blob/6a846703002d0b86dc54da56b39ddf7a22b271f5/lib/web_ui/lib/src/engine/semantics/semantics.dart#L422-L423
2. https://github.com/flutter/engine/blob/6a846703002d0b86dc54da56b39ddf7a22b271f5/lib/web_ui/lib/src/engine/semantics/semantics.dart#L1822
3. https://github.com/flutter/engine/blob/6a846703002d0b86dc54da56b39ddf7a22b271f5/lib/web_ui/lib/src/engine/semantics/semantics.dart#L1829