Function merged_row_width_in 

pub fn merged_row_width_in(width: f64) -> f64

What a row width wide keeps at its trailing end for the window’s furniture: everything merged_row_width names while the bar is wider than a phone’s, and the window’s own controls alone where it is not. A bar that narrow is the app’s row, and the room its own controls need there is worth more than the window’s search and new-tab door, which such a row draws for itself (its own search control, its own tabs +).