Don't create layout objects for children of display-none iframes.

third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.h

 /*
  * Copyright (C) 2006, 2007, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 68 matching lines @@
   void setContentFrame(Frame&) override;
   void clearContentFrame() override;
   void dispatchLoad() override;
   SandboxFlags getSandboxFlags() const override { return m_sandboxFlags; }
   bool canRenderFallbackContent() const override { return false; }
   void renderFallbackContent() override {}
   ScrollbarMode scrollingMode() const override { return ScrollbarAuto; }
   int marginWidth() const override { return -1; }
   int marginHeight() const override { return -1; }
   bool allowFullscreen() const override { return false; }
+  bool isDisplayNone() const override { return !layoutObject(); }
   AtomicString csp() const override { return nullAtom; }
   const WebVector<WebPermissionType>& delegatedPermissions() const override;
 
+  // Element overrides:
+  void setLayoutObject(LayoutObject*) override;
+
   DECLARE_VIRTUAL_TRACE();
 
  protected:
   HTMLFrameOwnerElement(const QualifiedName& tagName, Document&);
   void setSandboxFlags(SandboxFlags);
 
   bool loadOrRedirectSubframe(const KURL&,
                               const AtomicString& frameName,
                               bool replaceCurrentItem);
   bool isKeyboardFocusable() const override;
 
   void disposeWidgetSoon(Widget*);
+  void frameOwnerPropertiesChanged();
 
  private:
   // Intentionally private to prevent redundant checks when the type is
   // already HTMLFrameOwnerElement.
   bool isLocal() const override { return true; }
   bool isRemote() const override { return false; }
 
   bool isFrameOwnerElement() const final { return true; }
 
   virtual ReferrerPolicy referrerPolicyAttribute() {
@@ skipping 42 matching lines @@
 
 DEFINE_TYPE_CASTS(HTMLFrameOwnerElement,
                   FrameOwner,
                   owner,
                   owner->isLocal(),
                   owner.isLocal());
 
 }  // namespace blink
 
 #endif  // HTMLFrameOwnerElement_h