[Reland #1] Don't create layout objects for children of display-none iframes.

third_party/WebKit/Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 4772 matching lines @@
   }
 
   // Don't throttle display:none frames (see updateRenderThrottlingStatus).
   HTMLFrameOwnerElement* ownerElement = m_frame->deprecatedLocalOwner();
   if (m_hiddenForThrottling && ownerElement && !ownerElement->layoutObject()) {
     // No need to notify children because descendants of display:none frames
     // should remain throttled.
     updateRenderThrottlingStatus(m_hiddenForThrottling, m_subtreeThrottled,
                                  DontForceThrottlingInvalidation,
                                  DontNotifyChildren);
-    DCHECK(!canThrottleRendering());
   }
 
   for (Frame* child = m_frame->tree().firstChild(); child;
        child = child->tree().nextSibling()) {
     if (!child->isLocalFrame())
       continue;
     if (FrameView* view = toLocalFrame(child)->view())
       view->updateViewportIntersectionsForSubtree(targetState);
   }
 }
@@ skipping 458 matching lines @@
 void FrameView::setAnimationHost(
     std::unique_ptr<CompositorAnimationHost> host) {
   m_animationHost = std::move(host);
 }
 
 LayoutUnit FrameView::caretWidth() const {
   return LayoutUnit(getHostWindow()->windowToViewportScalar(1));
 }
 
 }  // namespace blink