While WebVR scenes can be viewed in a browser, their intended target is the vr headset, where the "dragging" is not at issue, and you are turning the view by turning your head. I think it would make more sense to keep the reverse dragging and change the mouse icon here. The intended experience is not "here is a scene that you can drag around" but "here is a virtual scene you are standing in and you can look left and right". So the intended context is that, headset or not, you are controlling the viewers head.