Replace style sharing cousin list search with LRU

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index a5dddea9ff27a0d1ab8a4d19beb42ad0897e3fd2..f81d7d1b89fdb327f9308aa0841dccd016e2ad5b 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -1680,8 +1680,10 @@ void Document::recalcStyle(StyleChange change)
         m_inStyleRecalc = false;
 
         // Pseudo element removal and similar may only work with these flags still set. Reset them after the style recalc.
-        if (m_styleResolver)
+        if (m_styleResolver) {
             m_styleSheetCollection->resetCSSFeatureFlags(m_styleResolver->ruleFeatureSet());
+            m_styleResolver->clearStyleSharingList();

[esprehn, 2013/08/22 17:33:02]

I think it'd make more sense to clear it at the start of ::recalcStyle since
then you know it's always correct inside there. That'd also mean you wouldn't
need the other clear() calls.

+        }
 
         if (frameView) {
             frameView->resumeScheduledEvents();
@@ -1930,6 +1932,8 @@ void Document::detach(const AttachContext& context)
     ContainerNode::detach(context);
 
     unscheduleStyleRecalc();
+    if (m_styleResolver)
+        m_styleResolver->clearStyleSharingList();

[esprehn, 2013/08/22 17:33:02]

Why doesn't this function just call clearStyleResolver() ? It's not clear why we
even need a style resolver if the RenderView is destroyed (you can't recalcStyle
then anyway).

 
     if (render)
         render->destroy();