Initial support for dynamic properties

lib/browser/api/touch-bar.js

@@ -14,6 +14,9 @@ class TouchBar extends EventEmitter {
     this.ordereredItems = []
     const registerItem = (item) => {
       this.items[item.id] = item
+      item.on('change', () => {
+        this.emit('change', item.id, item.type)
+      })
       if (item.child instanceof TouchBar) {
         item.child.ordereredItems.forEach(registerItem)
       }
@@ -35,8 +38,9 @@ class TouchBar extends EventEmitter {
   }
 }
 
-class TouchBarItem {
+class TouchBarItem extends EventEmitter {
   constructor (config) {
+    super()
     this.id = `${itemIdIncrementor++}`
   }
 }
@@ -81,7 +85,16 @@ TouchBar.Label = class TouchBarLabel extends TouchBarItem {
   constructor (config) {
     super(config)
     this.type = 'label'
-    this.label = config.label
+    this._label = config.label
+  }
+
+  set label (newLabel) {
+    this._label = newLabel
+    this.emit('change')
+  }
+
+  get label () {
+    return this._label
   }
 }