private static void setViewportLocked(
     DisplayViewport viewport, LogicalDisplay display, DisplayDevice device) {
   viewport.valid = true;
   viewport.displayId = display.getDisplayIdLocked();
   device.populateViewportLocked(viewport);
 }
 private void clearViewportsLocked() {
   mDefaultViewport.valid = false;
   mExternalTouchViewport.valid = false;
 }