[ts] Type-check ui/ResizerWidget.js with TypeScript

[email protected]

Bug: chromium:1011811
Change-Id: I0cc4fcc06b33c715d1a8ee642c91b54e395f8b14
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2351781
Reviewed-by: Jack Franklin <[email protected]>
Commit-Queue: Simon Zünd <[email protected]>
diff --git a/front_end/ui/SplitWidget.js b/front_end/ui/SplitWidget.js
index d83fb24..229b3c4 100644
--- a/front_end/ui/SplitWidget.js
+++ b/front_end/ui/SplitWidget.js
@@ -818,14 +818,14 @@
    * @param {!Element} resizerElement
    */
   installResizer(resizerElement) {
-    this._resizerWidget.addElement(resizerElement);
+    this._resizerWidget.addElement(/** @type {!HTMLElement} */ (resizerElement));
   }
 
   /**
    * @param {!Element} resizerElement
    */
   uninstallResizer(resizerElement) {
-    this._resizerWidget.removeElement(resizerElement);
+    this._resizerWidget.removeElement(/** @type {!HTMLElement} */ (resizerElement));
   }
 
   /**