Do not create toolbar item on the subsequent connectedCallback invocations

Otherwise we end up with repeated icons.

Bug: 400939386
Change-Id: I2f6b886262b7e5374c28c21dfacfd26bbaf00847
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6328141
Auto-Submit: Danil Somsikov <[email protected]>
Commit-Queue: Danil Somsikov <[email protected]>
Reviewed-by: Alex Rudenko <[email protected]>

Author: danilsomsikov

front_end/ui/legacy/Toolbar.ts

@@ -866,6 +866,9 @@ class ToolbarInputElement extends HTMLElement {
   datalist: HTMLDataListElement|null = null;
 
   connectedCallback(): void {
+    if (this.item) {
+      return;
+    }
     const list = this.getAttribute('list');
     if (list) {
       this.datalist = (this.getRootNode() as ShadowRoot | Document).querySelector(`datalist[id="${list}"]`);