Support display: contents for elements, first-line and first-letter pseudos.

third_party/WebKit/Source/core/dom/NodeComputedStyle.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2008 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 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
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #ifndef NodeComputedStyle_h
 #define NodeComputedStyle_h
 
+#include "core/dom/Element.h"
 #include "core/dom/LayoutTreeBuilderTraversal.h"
 #include "core/dom/Node.h"
 #include "core/dom/shadow/InsertionPoint.h"
 #include "core/html/HTMLOptGroupElement.h"
 #include "core/layout/LayoutObject.h"
 #include "core/style/ComputedStyle.h"
 
 namespace blink {
 
 inline const ComputedStyle* Node::computedStyle() const {
   return mutableComputedStyle();
 }
 
 inline ComputedStyle* Node::mutableComputedStyle() const {
   if (LayoutObject* layoutObject = this->layoutObject())
     return layoutObject->mutableStyle();
-  // <option> and <optgroup> can be styled even if they don't get layout
-  // objects, so they store their style internally and return it through
-  // nonLayoutObjectComputedStyle().  We check here explicitly to avoid the
-  // virtual call in the common case.
-  if (isHTMLOptGroupElement(*this) || isHTMLOptionElement(this))
-    return nonLayoutObjectComputedStyle();
+
+  if (isElementNode()) {
+    if (ComputedStyle* style = toElement(this)->mutableDisplayContentsStyle())
+      return style;
+
+    // <option> and <optgroup> can be styled even if they don't get layout
+    // objects, so they store their style internally and return it through
+    // nonLayoutObjectComputedStyle().  We check here explicitly to avoid the
+    // virtual call in the common case.
+    if (isHTMLOptGroupElement(*this) || isHTMLOptionElement(this))
+      return nonLayoutObjectComputedStyle();

[rune, 2016/11/01 07:12:23]

Now we will have two different ways of persisting ComputedStyle without a
LayoutObject. Wouldn't it be better to use the same method for option/optgroup
and display:contents?

[emilio, 2016/11/01 15:46:31]

Yep, this was already in my mind. I'd prefer to do this as a followup though, if
that's fine.

+  }
+
   return 0;
 }
 
 inline const ComputedStyle* Node::parentComputedStyle() const {
   if (isSlotOrActiveInsertionPoint())
     return 0;
   ContainerNode* parent = LayoutTreeBuilderTraversal::parent(*this);
   return parent ? parent->computedStyle() : 0;
 }
 
 inline const ComputedStyle& Node::computedStyleRef() const {
   const ComputedStyle* style = computedStyle();
   DCHECK(style);
   return *style;
 }
 
 }  // namespace blink
 #endif  // NodeComputedStyle_h