PlzNavigate: fix timing issue in app window creation

extensions/browser/app_window/app_window_contents.cc

Index: extensions/browser/app_window/app_window_contents.cc
diff --git a/extensions/browser/app_window/app_window_contents.cc b/extensions/browser/app_window/app_window_contents.cc
index 181e211dcd736d3fc7a1a61f5842547ac77ee843..03629988e967409ab66c987eee21555072a5ffbb 100644
--- a/extensions/browser/app_window/app_window_contents.cc
+++ b/extensions/browser/app_window/app_window_contents.cc
@@ -118,6 +118,12 @@ bool AppWindowContentsImpl::OnMessageReceived(const IPC::Message& message) {
   return handled;
 }
 
+void AppWindowContentsImpl::ReadyToCommitNavigation(
+    content::NavigationHandle* handle) {
+  if (!is_window_ready_)
+    host_->OnReadyToCommitFirstNavigation();
+}
+
 void AppWindowContentsImpl::UpdateDraggableRegions(
     const std::vector<DraggableRegion>& regions) {
   host_->UpdateDraggableRegions(regions);