Support invalidation sets for simple class selectors.

Source/core/css/RuleFeature.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 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 35 matching lines @@
 static bool isSkippableComponentForInvalidation(const CSSSelector& selector)
 {
     if (selector.matchesPseudoElement() || selector.pseudoType() == CSSSelector::PseudoHost)
         return false;
     return true;
 }
 
 // This method is somewhat conservative in what it acceptss.
 static bool supportsClassDescendantInvalidation(const CSSSelector& selector)
 {
     bool foundDescendantRelation = false;

[chrishtr, 2014/02/19 17:50:44]

remove these variables

[rune, 2014/02/19 18:47:40]

See other comment.

-    bool foundAncestorIdent = false;
     bool foundIdent = false;
     for (const CSSSelector* component = &selector; component; component = component->tagHistory()) {
 
         // FIXME: We should allow pseudo elements, but we need to change how they hook
         // into recalcStyle by moving them to recalcOwnStyle instead of recalcChildStyle.
 
         // FIXME: next up: Tag and Id.
         if (component->m_match == CSSSelector::Class) {
             if (!foundDescendantRelation)
                 foundIdent = true;

[chrishtr, 2014/02/19 17:50:44]

return true, remove if (!foundDescendantRelation)

[rune, 2014/02/19 18:47:40]

We still need to continue to look for adjacent combinators and
!isSkippableComponentForInvalidation() for which we need to return false even if
foundIdent is true.

[chrishtr, 2014/02/19 18:54:01]

Oh right, good point.

-            else
-                foundAncestorIdent = true;
         } else if (!isSkippableComponentForInvalidation(*component)) {
             return false;
         }
         // FIXME: We can probably support ChildTree and DescendantTree.
         switch (component->relation()) {
         case CSSSelector::Descendant:
         case CSSSelector::Child:
             foundDescendantRelation = true;

[chrishtr, 2014/02/19 17:50:44]

return true;

             // Fall through!
         case CSSSelector::SubSelector:
             continue;
         default:
             return false;
         }
     }
-    return foundDescendantRelation && foundAncestorIdent && foundIdent;
+    return foundIdent;

[chrishtr, 2014/02/19 17:50:44]

remove this line

[rune, 2014/02/19 18:47:40]

See other comment.

 }
 
 void extractClassIdOrTag(const CSSSelector& selector, Vector<AtomicString>& classes, AtomicString& id, AtomicString& tagName)
 {
     if (selector.m_match == CSSSelector::Tag)
         tagName = selector.tagQName().localName();
     else if (selector.m_match == CSSSelector::Id)
         id = selector.value();
     else if (selector.m_match == CSSSelector::Class)
         classes.append(selector.value());
@@ skipping 328 matching lines @@
         element->setNeedsStyleRecalc(LocalStyleChange);
 
     invalidationClasses.remove(oldSize, invalidationClasses.size() - oldSize);
     element->clearChildNeedsStyleInvalidation();
     element->clearNeedsStyleInvalidation();
 
     return thisElementNeedsStyleRecalc;
 }
 
 } // namespace WebCore