widget: remove unused Button.prevClicks

It was left over from a previous approach to enable the program
to decide the ordering between calls to Layout vs Clicked.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

widget/button.go

@@ -15,9 +15,6 @@ type Button struct {
 	click gesture.Click
 	// clicks tracks the number of unreported clicks.
 	clicks  int
-	// prevClicks tracks the number of unreported clicks
-	// that belong to the previous frame.
-	prevClicks int
 	history []Click
 }
 
@@ -31,9 +28,6 @@ func (b *Button) Clicked(gtx *layout.Context) bool {
 	b.processEvents(gtx)
 	if b.clicks > 0 {
 		b.clicks--
-		if b.prevClicks > 0 {
-			b.prevClicks--
-		}
 		if b.clicks > 0 {
 			// Ensure timely delivery of remaining clicks.
 			op.InvalidateOp{}.Add(gtx.Ops)
@@ -49,8 +43,6 @@ func (b *Button) History() []Click {
 
 func (b *Button) Layout(gtx *layout.Context) {
 	// Flush clicks from before the previous frame.
-	b.clicks -= b.prevClicks
-	b.prevClicks = 0
 	b.processEvents(gtx)
 	b.click.Add(gtx.Ops)
 	for len(b.history) > 0 {