Support getComputedStyle for non-rendered pseudo elements.

Source/core/css/resolver/StyleResolver.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 758 matching lines @@
     StyleResolverParentScope::ensureParentStackIsPushed();
 
     if (pseudoStyleRequest.allowsInheritance(state.parentStyle())) {
         state.setStyle(RenderStyle::create());
         state.style()->inheritFrom(state.parentStyle());
     } else {
         state.setStyle(defaultStyleForElement());
         state.setParentStyle(RenderStyle::clone(state.style()));
     }
 
+    state.style()->setStyleType(pseudoStyleRequest.pseudoId);
     state.fontBuilder().initForStyleResolve(state.document(), state.style());
 
     // Since we don't use pseudo-elements in any of our quirk/print
     // user agent rules, don't waste time walking those rules.
 
     {
         // Check UA, user and author rules.
         ElementRuleCollector collector(state.elementContext(), m_selectorFilter, state.style());
         collector.setPseudoStyleRequest(pseudoStyleRequest);
 
         matchUARules(collector);
         matchAuthorRules(state.element(), collector, false);
 
         if (collector.matchedResult().matchedProperties.isEmpty())
             return false;
 
-        state.style()->setStyleType(pseudoStyleRequest.pseudoId);
-
         applyMatchedProperties(state, collector.matchedResult());
         applyCallbackSelectors(state);
 
         addContentAttrValuesToFeatures(state.contentAttrValues(), m_features);
     }
 
     // Cache our original display.
     state.style()->setOriginalDisplay(state.style()->display());
 
     // FIXME: Passing 0 as the Element* introduces a lot of complexity
@@ skipping 14 matching lines @@
     return true;
 }
 
 PassRefPtr<RenderStyle> StyleResolver::pseudoStyleForElement(Element* element, const PseudoStyleRequest& pseudoStyleRequest, RenderStyle* parentStyle)
 {
     ASSERT(parentStyle);
     if (!element)
         return nullptr;
 
     StyleResolverState state(document(), element, parentStyle);
-    if (!pseudoStyleForElementInternal(*element, pseudoStyleRequest, parentStyle, state))
-        return nullptr;
+    if (!pseudoStyleForElementInternal(*element, pseudoStyleRequest, parentStyle, state)) {
+        if (pseudoStyleRequest.type == PseudoStyleRequest::ForRenderer)

[esprehn, 2014/09/17 19:04:42]

This doesn't make sense, pseudoStyleForElementInternal only returns false if
there's no matched properties. If there's no matched properties then you're just
returning the default UA style here. I don't think you're returning the correct
style...

[rune, 2014/09/17 20:00:33]

http://www.w3.org/TR/CSS2/generate.html#before-after-content:

"The :before and :after pseudo-elements inherit any inheritable properties from
the element in the document tree to which they are attached."
"In a :before or :after pseudo-element declaration, non-inherited properties
take their initial values."

That is exactly what happens in:

https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

+            return nullptr;
+        return state.takeStyle();
+    }
 
     if (PseudoElement* pseudoElement = element->pseudoElement(pseudoStyleRequest.pseudoId))
         setAnimationUpdateIfNeeded(state, *pseudoElement);
 
     // Now return the style.
     return state.takeStyle();
 }
 
 PassRefPtr<RenderStyle> StyleResolver::styleForPage(int pageIndex)
 {
@@ skipping 749 matching lines @@
     visitor->trace(m_uncommonAttributeRuleSet);
     visitor->trace(m_watchedSelectorsRules);
     visitor->trace(m_treeBoundaryCrossingRules);
     visitor->trace(m_styleSharingLists);
     visitor->trace(m_pendingStyleSheets);
     visitor->trace(m_document);
 #endif
 }
 
 } // namespace blink