Add missing return types for function parameters in ui/

These are required for the upcoming TypeScript 3.9.2 upgrade.

[email protected]

Bug: 1011811
Change-Id: Ibb7000f4c70863549bf6ce160a9fb89cb163e6f7
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2199122
Commit-Queue: Jack Franklin <[email protected]>
Reviewed-by: Jack Franklin <[email protected]>
Auto-Submit: Tim van der Lippe <[email protected]>
diff --git a/front_end/ui/Widget.js b/front_end/ui/Widget.js
index 8c86d3f..2e2fc1e 100644
--- a/front_end/ui/Widget.js
+++ b/front_end/ui/Widget.js
@@ -166,7 +166,7 @@
   }
 
   /**
-   * @param {function(this:Widget)} method
+   * @param {function(this:Widget):void} method
    */
   _callOnVisibleChildren(method) {
     const copy = this._children.slice();
@@ -218,7 +218,7 @@
   }
 
   /**
-   * @param {function(this:Widget)} notification
+   * @param {function(this:Widget):void} notification
    */
   _notify(notification) {
     ++this._notificationDepth;
@@ -718,7 +718,7 @@
  */
 export class VBoxWithResizeCallback extends VBox {
   /**
-   * @param {function()} resizeCallback
+   * @param {function():void} resizeCallback
    */
   constructor(resizeCallback) {
     super();