Files.app: Fix broken js-comp by casting details panel to HTMLElement.

ui/file_manager/file_manager/foreground/js/import_controller.js

Index: ui/file_manager/file_manager/foreground/js/import_controller.js
diff --git a/ui/file_manager/file_manager/foreground/js/import_controller.js b/ui/file_manager/file_manager/foreground/js/import_controller.js
index fac4e6d4fdac8a8a6a74f7b0820afa5fe18024df..a179c2abad9c826e160aca8f3dd4c7f1aab7a904 100644
--- a/ui/file_manager/file_manager/foreground/js/import_controller.js
+++ b/ui/file_manager/file_manager/foreground/js/import_controller.js
@@ -559,7 +559,9 @@ importer.RuntimeCommandWidget.prototype.setDetailsVisible_ = function(visible) {
   } else {
     this.detailsPanel_.className = 'hidden';
     // transition duration is 200ms. Let's wait for 400ms.
-    ensureTransitionEndEvent(this.detailsPanel_, 400);
+    ensureTransitionEndEvent(
+        /** @type {!HTMLElement} */ (this.detailsPanel_),
+        400);
   }
 };