Speculative fix for PopupMenuTest flakiness

content/browser/site_per_process_browsertest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/site_per_process_browsertest.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 6395 matching lines @@
       embedded_test_server()->GetURL("/cross_site_iframe_factory.html?a(a)"));
   EXPECT_TRUE(NavigateToURL(shell(), main_url));
 
   FrameTreeNode* root = web_contents()->GetFrameTree()->root();
 
 #if !defined(OS_MACOSX) && !defined(OS_ANDROID)
   // Unused variable on Mac and Android.
   RenderWidgetHostViewBase* rwhv_root = static_cast<RenderWidgetHostViewBase*>(
       root->current_frame_host()->GetRenderWidgetHost()->GetView());
 #endif
-  web_contents()->SendScreenRects();
 
-  content::TestNavigationObserver navigation_observer(shell()->web_contents());
   FrameTreeNode* child_node = root->child_at(0);
   GURL site_url(embedded_test_server()->GetURL(
       "baz.com", "/site_isolation/page-with-select.html"));
   NavigateFrameToURL(child_node, site_url);
-  navigation_observer.Wait();
+
+  web_contents()->SendScreenRects();
+
+  WaitForChildFrameSurfaceReady(child_node->current_frame_host());
 
   RenderWidgetHostViewBase* rwhv_child = static_cast<RenderWidgetHostViewBase*>(
       child_node->current_frame_host()->GetRenderWidgetHost()->GetView());
 
   EXPECT_NE(shell()->web_contents()->GetSiteInstance(),
             child_node->current_frame_host()->GetSiteInstance());
 
   scoped_refptr<ShowWidgetMessageFilter> filter = new ShowWidgetMessageFilter();
   child_node->current_frame_host()->GetProcess()->AddFilter(filter.get());
 
@@ skipping 3711 matching lines @@
   // the body of the page.
   std::string body;
   EXPECT_TRUE(ExecuteScriptAndExtractString(root->child_at(0), R"(
     var body = document.getElementsByTagName('pre')[0].innerText;
     window.domAutomationController.send(body);)",
                                             &body));
   EXPECT_EQ("my_token=my_value\n", body);
 }
 
 }  // namespace content