don't start long press when selecting text

The timers to initiate short press and long press shouldn't
be started if text is selected. Since these presses won't
provide any feedback (e.g., the context menu doesn't show
up), with them disabled, the long press can turn into a
drag.

bug:34403750
Change-Id: I019796334a8f3090922747ae3c9e21d3b87b4a3c