[css-display] Support display: contents pseudo-elements.

third_party/WebKit/Source/core/layout/LayoutObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved.
  *               (http://www.torchmobile.com/)
@@ skipping 156 matching lines @@
       image->setIsGeneratedContent();
     } else {
       image->setImageResource(LayoutImageResource::create());
     }
     image->setStyleInternal(nullptr);
     return image;
   }
 
   switch (style.display()) {
     case EDisplay::None:
+      return nullptr;
     case EDisplay::Contents:
-      return nullptr;
+      if (LIKELY(!element->isPseudoElement()))
+        return nullptr;
+    // fall through
     case EDisplay::Inline:
       return new LayoutInline(element);
     case EDisplay::Block:
     case EDisplay::FlowRoot:
     case EDisplay::InlineBlock:
       if (RuntimeEnabledFeatures::layoutNGEnabled())
         return new LayoutNGBlockFlow(element);
       return new LayoutBlockFlow(element);
     case EDisplay::ListItem:
       return new LayoutListItem(element);
@@ skipping 2823 matching lines @@
   if (RefPtr<ComputedStyle> style = firstLineStyleForCachedUncachedType(
           Cached, isText() ? parent() : this, m_style.get()))
     return style.get();
 
   return m_style.get();
 }
 
 ComputedStyle* LayoutObject::getCachedPseudoStyle(
     PseudoId pseudo,
     const ComputedStyle* parentStyle) const {
+  DCHECK_NE(pseudo, PseudoIdBefore);
+  DCHECK_NE(pseudo, PseudoIdAfter);
+
   if (pseudo < FirstInternalPseudoId && !style()->hasPseudoStyle(pseudo))
     return nullptr;
 
   ComputedStyle* cachedStyle = style()->getCachedPseudoStyle(pseudo);
   if (cachedStyle)
     return cachedStyle;
 
   RefPtr<ComputedStyle> result =
       getUncachedPseudoStyle(PseudoStyleRequest(pseudo), parentStyle);
   if (result)
@@ skipping 497 matching lines @@
     const blink::LayoutObject* root = object1;
     while (root->parent())
       root = root->parent();
     root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
   } else {
     WTFLogAlways("%s", "Cannot showLayoutTree. Root is (nil)");
   }
 }
 
 #endif