Codechange: Call Widget::SetDirty/SetLowered directly. (#11417)

In these instances we already have the widget to hand, so don't need to look it up by index again.

src/widgets/dropdown.cpp

@@ -438,9 +438,9 @@ void ShowDropDownList(Window *w, DropDownList &&list, int selected, int button,
 	if ((nwi->type & WWT_MASK) == NWID_BUTTON_DROPDOWN) {
 		nwi->disp_flags |= ND_DROPDOWN_ACTIVE;
 	} else {
-		w->LowerWidget(button);
+		nwi->SetLowered(true);
 	}
-	w->SetWidgetDirty(button);
+	nwi->SetDirty(w);
 
 	if (width != 0) {
 		if (_current_text_dir == TD_RTL) {

src/window.cpp

@@ -228,7 +228,7 @@ void Window::DisableAllWidgetHighlight()
 
 		if (nwid->IsHighlighted()) {
 			nwid->SetHighlighted(TC_INVALID);
-			this->SetWidgetDirty(i);
+			nwid->SetDirty(this);
 		}
 	}
 
@@ -248,7 +248,7 @@ void Window::SetWidgetHighlight(byte widget_index, TextColour highlighted_colour
 	if (nwid == nullptr) return;
 
 	nwid->SetHighlighted(highlighted_colour);
-	this->SetWidgetDirty(widget_index);
+	nwid->SetDirty(this);
 
 	if (highlighted_colour != TC_INVALID) {
 		/* If we set a highlight, the window has a highlight */