Don't bother layout until first navigation is done.

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

Index: third_party/WebKit/Source/web/tests/sim/SimWebViewClient.h
diff --git a/third_party/WebKit/Source/web/tests/sim/SimWebViewClient.h b/third_party/WebKit/Source/web/tests/sim/SimWebViewClient.h
index 40474d84f67674e2b1a270881091f34d29c4592d..6ebb17992eaea51c11ced8359c6c877198b4662d 100644
--- a/third_party/WebKit/Source/web/tests/sim/SimWebViewClient.h
+++ b/third_party/WebKit/Source/web/tests/sim/SimWebViewClient.h
@@ -16,6 +16,9 @@ public:
     explicit SimWebViewClient(WebLayerTreeView&);
 
     WebLayerTreeView* layerTreeView() override { return m_layerTreeView; }
+    void didUpdateLayout() override { m_hadFirstLayout = true; }
+
+    bool hadFirstLayout() const { return m_hadFirstLayout; }
 
     bool hadVisuallyNonEmptyLayout() const { return m_hadVisuallyNonEmptyLayout; }
     bool hadFinishedParsingLayout() const { return m_hadFinishedParsingLayout; }
@@ -30,6 +33,7 @@ private:
     bool m_hadFinishedLoadingLayout;
 
     WebLayerTreeView* m_layerTreeView;
+    bool m_hadFirstLayout = false;
 };
 
 } // namespace blink