Use case

In AppBarTheme I can provide the toolbarHeight.
But since app bar leading width uses the constant kToolbarHeight by default it is no longer a square because toolbar height is changed in the theme.

On Design Device (toolbar height 56):

On iPad 13inch (toolbar height scaled to 90 based on custom logic):

Proposal

1. Either leadingWidth should use toolbar height from theme internally
2. Or I should be able to provide leadingWidth in AppBarTheme along with toolbarHeight