That's not so useful per-se on iOS, as iOS has a full set of zooming features, that range from double-tap-with-three-fingers to activate zooming mode, to the al

That's not so useful per-se on iOS, as iOS has a full set of zooming features, that range from double-tap-with-three-fingers to activate zooming mode, to the always-on-top zoom controller that popups a menu with several options, including which filters to apply in the zooming window (eg: contrast, b&w). These features work across the whole operating system, so in all apps, not just the browser.