As seen in many webkit based browsers (ipad browser safari, android browser, chrome) zoom to content is a good feature for small devices with touch support.
Just for reference, in the browsers that already support this feature the usage is as follows: double-tap zooms to content, double-tap in zoomed content zooms out.
This is implemented already in webkit-core , so it needs to be added in the API of webkit-gtk. It has been implemented for the QT API .
Upstream feature request for the Browser used in the Sugar learning platform .
macOS also has this via a double 2-finger tap on touchpad. The problem though
The problem here isn't WebCore, the problem here is that double 2-finger tap is opening and closing context menu, and double 1-finger tap (both on touchpad and touchscreen) is selecting the current word, so you would have to compromise on something.
In this case i would propose to align with the typical Android/iphone design for touch gestures. We should talk to Carlos i guess.