Prevent initial display of modal dialogs when loading.

remoting/webapp/main.css

Index: remoting/webapp/main.css
diff --git a/remoting/webapp/main.css b/remoting/webapp/main.css
index 9f551570d0302cfc589eb4939935653f851069d2..08e464ed2044987450a2d4924ea34e36e9865050 100644
--- a/remoting/webapp/main.css
+++ b/remoting/webapp/main.css
@@ -476,4 +476,12 @@ button {
 
 * {
   box-sizing: border-box;
-}
+}
+
+/*
+ * Setting hidden on elements that match some rule overriding 'display' doesn't
+ * do what you would expect unless this is made explicit (and !important).
+ */
+[hidden] {
+  display: none !important;
+}