Method onBubblesChanged

tools/xsbug/MessagePane.js:225–228

(button)

		IconButton($, { top:0, variant:5, active:true, visible:false, 
			Behavior: class extends ButtonBehavior {
				onBubblesChanged(button) {
					button.active = model.canClearAllBubbles();
					this.changeState(button, button.active ? 1 : 0);
				}
				onTap(button) {
					model.doClearAllBubbles();
				}