Convert ui/ to ESM

- ViewManager has been extracted from View
- Action has been extracted from ActionRegistry
- ContextFlavorListener has been extracted from Context

Bug: 1006759
Change-Id: Iff41f3a7db4dcbd6da90fd5752923e32af03bac8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1827294
Commit-Queue: Tim Van der Lippe <[email protected]>
Reviewed-by: Yang Guo <[email protected]>
Cr-Original-Commit-Position: refs/heads/master@{#702390}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 0ffd51ccac853da7c8ec3d91ae868bc61626b29b
diff --git a/front_end/ui/EmptyWidget.js b/front_end/ui/EmptyWidget.js
index 4dee094..71872f8 100644
--- a/front_end/ui/EmptyWidget.js
+++ b/front_end/ui/EmptyWidget.js
@@ -31,7 +31,7 @@
 /**
  * @unrestricted
  */
-UI.EmptyWidget = class extends UI.VBox {
+export default class EmptyWidget extends UI.VBox {
   /**
    * @param {string} text
    */
@@ -65,4 +65,13 @@
   set text(text) {
     this._textElement.textContent = text;
   }
-};
+}
+
+/* Legacy exported object*/
+self.UI = self.UI || {};
+
+/* Legacy exported object*/
+UI = UI || {};
+
+/** @constructor */
+UI.EmptyWidget = EmptyWidget;