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

third_party/WebKit/Source/core/svg/SVGElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Nikolas Zimmermann
  * <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2008 Rob Buis <buis@kde.org>
  * Copyright (C) 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Alp Toker <alp@atoker.com>
  * Copyright (C) 2009 Cameron McCormack <cam@mcc.id.au>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 1003 matching lines @@
   if (!correspondingElement())
     return document().ensureStyleResolver().styleForElement(this);
 
   const ComputedStyle* style = nullptr;
   if (Element* parent = parentOrShadowHostElement()) {
     if (LayoutObject* layoutObject = parent->layoutObject())
       style = layoutObject->style();
   }
 
   return document().ensureStyleResolver().styleForElement(
-      correspondingElement(), style, DisallowStyleSharing);
+      correspondingElement(), style, style, DisallowStyleSharing);

[rune, 2017/01/27 13:09:23]

Is this correct? Can we get here for SVGSVGElement being a child of some
display:contents html element?

[emilio, 2017/01/27 22:13:15]

Note that style will only be non-null when the parent element has a layout
object, so I think this is correct (though somewhat suboptimal I guess).

[rune, 2017/02/06 22:40:44]

The display property applies to SVG elements, but with a special interpretation
[1]. It should be clarified what display:contents means for SVG. If
display:contents skips creating layout boxes for SVG as well, the code above is
wrong. Make some tests to see what happens with your implementation. It looks
like display:content for a USE parent will cause the layoutObject to be null for
that parent and cause strangeness here?

Would it be best to override layoutObjectIsNeeded() to return true for
display:contents for SVG elements for now?

[1] https://www.w3.org/TR/SVG/painting.html#DisplayProperty

[emilio, 2017/02/08 10:59:24]

Makes sense, will do.

 }
 
 MutableStylePropertySet* SVGElement::animatedSMILStyleProperties() const {
   if (hasSVGRareData())
     return svgRareData()->animatedSMILStyleProperties();
   return nullptr;
 }
 
 MutableStylePropertySet* SVGElement::ensureAnimatedSMILStyleProperties() {
   return ensureSVGRareData()->ensureAnimatedSMILStyleProperties();
@@ skipping 252 matching lines @@
   visitor->trace(m_className);
   Element::trace(visitor);
 }
 
 const AtomicString& SVGElement::eventParameterName() {
   DEFINE_STATIC_LOCAL(const AtomicString, evtString, ("evt"));
   return evtString;
 }
 
 }  // namespace blink