Prevent repeated taps from resetting insertion handle position

Prevent repeated taps from resetting insertion handle position

Repeated longpress and tap gestures were resetting the cached handle positions
in anticipation of receiving updated values from the renderer.  However, if
the gesture failed to change the selection position, no update was received, and
subsequent taps on the handle would improperly position the paste popup at the
reset position.  Fix this by avoiding cached position resets when the insertion
or selection is already active.

BUG=399222