This directory contains browser side input event handling code.
In order for pages to override the behaviour of touchpad pinch zooming, we offer synthetic wheel events that may be canceled. The TouchpadPinchEventQueue accepts the gesture pinch events created from native events and sends the appropriate wheel events to the renderer. Once the renderer has acknowledged a wheel event, we offer the corresponding gesture pinch event back to the client of the TouchpadPinchEventQueue. If the pinch has not been consumed by the page, the client may go on to send the actual gesture pinch event to the renderer which will perform the pinch zoom.
Note that for touchscreen gesture pinch events, there is no need for a similar queue as touch events would have already been offered to the renderer before being recognized as a pinch gesture.
See issue 289887 for the discussion on offering wheel events for touchpad pinch.
Touchpad pinch zoom design doc.