make top-content component and frame-content component

src/content/components/frame-content.js

@@ -0,0 +1,16 @@
+import CommonComponent from './common';
+
+export default class FrameContent {
+
+  constructor(win, store) {
+    this.children = [new CommonComponent(win, store)];
+  }
+
+  update() {
+    this.children.forEach(c => c.update());
+  }
+
+  onMessage(message) {
+    this.children.forEach(c => c.onMessage(message));
+  }
+}