Defer pushing the parent stack in recalcStyle until StyleResolver::styleForElement()

Source/core/dom/Element.cpp

Index: Source/core/dom/Element.cpp
diff --git a/Source/core/dom/Element.cpp b/Source/core/dom/Element.cpp
index cca4eab671f19e85afd63d5b385d881983ffa15d..21fadd0eb9d882d1a0049a3b5f5518f0740072ad 100644
--- a/Source/core/dom/Element.cpp
+++ b/Source/core/dom/Element.cpp
@@ -40,6 +40,7 @@
 #include "core/css/PropertySetCSSStyleDeclaration.h"
 #include "core/css/StylePropertySet.h"
 #include "core/css/resolver/StyleResolver.h"
+#include "core/css/resolver/StyleResolverParentScope.h"
 #include "core/dom/Attr.h"
 #include "core/dom/CSSSelectorWatch.h"
 #include "core/dom/ClientRect.h"
@@ -104,40 +105,6 @@ namespace WebCore {
 using namespace HTMLNames;
 using namespace XMLNames;
 
-class StyleResolverParentPusher {
-public:
-    explicit StyleResolverParentPusher(Element& parent)
-        : m_parent(parent)
-        , m_pushedStyleResolver(0)
-    {
-    }
-    void push()
-    {
-        if (m_pushedStyleResolver)
-            return;
-        m_pushedStyleResolver = &m_parent.document().ensureStyleResolver();
-        m_pushedStyleResolver->pushParentElement(m_parent);
-    }
-    ~StyleResolverParentPusher()
-    {
-
-        if (!m_pushedStyleResolver)
-            return;
-
-        // This tells us that our pushed style selector is in a bad state,
-        // so we should just bail out in that scenario.
-        ASSERT(m_pushedStyleResolver == m_parent.document().styleResolver());
-        if (m_pushedStyleResolver != m_parent.document().styleResolver())
-            return;
-
-        m_pushedStyleResolver->popParentElement(m_parent);
-    }
-
-private:
-    Element& m_parent;
-    StyleResolver* m_pushedStyleResolver;
-};
-
 typedef Vector<RefPtr<Attr> > AttrNodeList;
 typedef HashMap<Element*, OwnPtr<AttrNodeList> > AttrNodeListMap;
 
@@ -1365,8 +1332,6 @@ void Element::attach(const AttachContext& context)
 {
     ASSERT(document().inStyleRecalc());
 
-    StyleResolverParentPusher parentPusher(*this);
-
     // We've already been through detach when doing an attach, but we might
     // need to clear any state that's been added since then.
     if (hasRareData() && styleChangeType() == NeedsReattachStyleChange) {
@@ -1382,15 +1347,13 @@ void Element::attach(const AttachContext& context)
 
     addCallbackSelectors();
 
-    createPseudoElementIfNeeded(BEFORE);
+    StyleResolverParentScope parentScope(*this);
 
     // When a shadow root exists, it does the work of attaching the children.
-    if (ElementShadow* shadow = this->shadow()) {
-        parentPusher.push();
+    if (ElementShadow* shadow = this->shadow())
         shadow->attach(context);
-    } else if (firstChild()) {
-        parentPusher.push();
-    }
+
+    createPseudoElementIfNeeded(BEFORE);
 
     ContainerNode::attach(context);
 
@@ -1601,21 +1564,19 @@ void Element::recalcChildStyle(StyleRecalcChange change)
     ASSERT(change >= Inherit || childNeedsStyleRecalc());
     ASSERT(!needsStyleRecalc());
 
-    StyleResolverParentPusher parentPusher(*this);
+    StyleResolverParentScope parentScope(*this);
 
     for (ShadowRoot* root = youngestShadowRoot(); root; root = root->olderShadowRoot()) {
-        if (shouldRecalcStyle(change, root)) {
-            parentPusher.push();
+        if (shouldRecalcStyle(change, root))
             root->recalcStyle(change);
-        }
     }
 
-    if (shouldRecalcStyle(change, this))
-        updatePseudoElement(BEFORE, change);
-
     if (change < Force && hasRareData() && childNeedsStyleRecalc())
         checkForChildrenAdjacentRuleChanges();
 
+    if (shouldRecalcStyle(change, this))
+        updatePseudoElement(BEFORE, change);
+
     // This loop is deliberately backwards because we use insertBefore in the rendering tree, and want to avoid
     // a potentially n^2 loop to find the insertion point while resolving style. Having us start from the last
     // child and work our way back means in the common case, we'll find the insertion point in O(1) time.
@@ -1628,12 +1589,10 @@ void Element::recalcChildStyle(StyleRecalcChange change)
             lastTextNode = toText(child);
         } else if (child->isElementNode()) {
             Element* element = toElement(child);
-            if (shouldRecalcStyle(change, element)) {
-                parentPusher.push();
+            if (shouldRecalcStyle(change, element))
                 element->recalcStyle(change, lastTextNode);
-            } else if (element->supportsStyleSharing()) {
+            else if (element->supportsStyleSharing())
                 styleResolver.addToStyleSharingList(*element);
-            }
             if (element->renderer())
                 lastTextNode = 0;
         }