fixed Toast is briefly displayed on page load (#3725)

* fixed Toast is briefly displayed on page load

* updated fix for Toast is briefly displayed on page load

* updated the test html renderings

client-src/elements/chromedash-app.js

@@ -130,6 +130,11 @@ class ChromedashApp extends LitElement {
     this.drawerOpen = !IS_MOBILE;
   }
 
+  firstUpdated() {
+    const toastEl = document.createElement('chromedash-toast');
+    document.body.appendChild(toastEl);
+  }
+
   connectedCallback() {
     super.connectedCallback();
     this.loading = true;

pages/testdata/featurelist_test/test_html_rendering.html

@@ -158,8 +158,6 @@ limitations under the License.
     <chromedash-footer></chromedash-footer>
   </div>
 
-  <chromedash-toast msg="Welcome to chromestatus.com!"></chromedash-toast>
-
   
   <chromedash-legend></chromedash-legend>
 

pages/testdata/intentpreview_test/test_html_rendering.html

@@ -338,8 +338,6 @@ False
     <chromedash-footer></chromedash-footer>
   </div>
 
-  <chromedash-toast msg="Welcome to chromestatus.com!"></chromedash-toast>
-
   
 
   

pages/testdata/users_test/test_html_rendering.html

@@ -138,8 +138,6 @@ limitations under the License.
     <chromedash-footer></chromedash-footer>
   </div>
 
-  <chromedash-toast msg="Welcome to chromestatus.com!"></chromedash-toast>
-
   
 
   

templates/_base.html

@@ -126,8 +126,6 @@ limitations under the License.
     <chromedash-footer></chromedash-footer>
   </div>
 
-  <chromedash-toast msg="Welcome to chromestatus.com!"></chromedash-toast>
-
   {% block overlay %}{% endblock %}
 
   {% block js %}{% endblock %}

templates/spa.html

@@ -78,8 +78,6 @@ limitations under the License.
     bannerTime="{{banner_time}}">
   </chromedash-app>
 
-  <chromedash-toast msg="Welcome to chromestatus.com!"></chromedash-toast>
-
   <script src="https://www.googletagmanager.com/gtag/js?id=UA-179341418-1" async nonce="{{nonce}}"></script>
 
   {#