As a quick fix for  crbug.com/606938 , we are suppressing only the dispatch of MEs for a GestureTap event. Other related "side-effects", mouse focus, setting EventHandler states like m_clickNode etc is not affected.

Not clear what's the right behavior here: the side-effects are for TEs as well as for PEs. If we cancel all side-effects for canceled PEs, TE should be felt broken.