I decided to roll my own virtual keyboard after a protracted battle with inconsistencies and quirks across mobile browsers. The glaring difference is that the native keyboard slides the viewport upward on iOS (pushing the fixed header off screen), whereas it shrinks it on Android (causing relayout that repositions any UI element fixed to the bottom).

Also, notice how the search box is anchored to (and animates with) the virtual keyboard. This effect cannot even be achieved with the experimental VirtualKeyboard API, which is not supported by WebKit anyway.