Don't bother layout until first navigation is done.

third_party/WebKit/Source/web/tests/sim/SimWebViewClient.h

 // Copyright 2015 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.
 
 #ifndef SimWebViewClient_h
 #define SimWebViewClient_h
 
 #include "web/tests/FrameTestHelpers.h"
 
 namespace blink {
 
 class WebLayerTreeView;
 
 class SimWebViewClient final : public FrameTestHelpers::TestWebViewClient {
 public:
     explicit SimWebViewClient(WebLayerTreeView&);
 
     WebLayerTreeView* layerTreeView() override { return m_layerTreeView; }
+    void didUpdateLayout() override { m_hadFirstLayout = true; }
+
+    bool hadFirstLayout() const { return m_hadFirstLayout; }
 
     int visuallyNonEmptyLayoutCount() const { return m_visuallyNonEmptyLayoutCount; }
     int finishedParsingLayoutCount() const { return m_finishedParsingLayoutCount; }
     int finishedLoadingLayoutCount() const { return m_finishedLoadingLayoutCount; }
 
 private:
     // WebWidgetClient overrides.
     void didMeaningfulLayout(WebMeaningfulLayout) override;
 
     int m_visuallyNonEmptyLayoutCount;
     int m_finishedParsingLayoutCount;
     int m_finishedLoadingLayoutCount;
 
     WebLayerTreeView* m_layerTreeView;
+    bool m_hadFirstLayout = false;
 };
 
 } // namespace blink
 
 #endif