Clear StyleResolverState after each resolve.

Source/core/css/resolver/StyleResolver.cpp

Index: Source/core/css/resolver/StyleResolver.cpp
diff --git a/Source/core/css/resolver/StyleResolver.cpp b/Source/core/css/resolver/StyleResolver.cpp
index 74409ec01cca1d9e8d8e58d4e13f5fa4704dd5e1..48eb2c104c505b53690a2502f3ad32edd1aad715 100644
--- a/Source/core/css/resolver/StyleResolver.cpp
+++ b/Source/core/css/resolver/StyleResolver.cpp
@@ -1015,10 +1015,10 @@ PassRefPtr<RenderStyle> StyleResolver::styleForElement(Element* element, RenderS
     StyleResolverState& state = m_state;
     state.initForStyleResolve(document(), element, defaultParent, regionForStyling);
     if (sharingBehavior == AllowStyleSharing && !state.distributedToInsertionPoint()) {
-        RenderStyle* sharedStyle = locateSharedStyle();
+        RefPtr<RenderStyle> sharedStyle = locateSharedStyle();
         if (sharedStyle) {
             state.clear();
-            return sharedStyle;
+            return sharedStyle.release();
         }
     }
 
@@ -1069,15 +1069,13 @@ PassRefPtr<RenderStyle> StyleResolver::styleForElement(Element* element, RenderS
     // Clean up our style object's display and text decorations (among other fixups).
     adjustRenderStyle(state.style(), state.parentStyle(), element);
 
-    state.clear(); // Clear out for the next resolve.
-
     document()->didAccessStyleResolver();
 
     if (element->hasTagName(bodyTag))
         document()->textLinkColors().setTextColor(state.style()->visitedDependentColor(CSSPropertyColor));
 
-    // Now return the style.
-    return state.takeStyle();
+    // Now return the style and clear out for the next resolve.
+    return state.takeStyleAndClear();
 }
 
 PassRefPtr<RenderStyle> StyleResolver::styleForKeyframe(const RenderStyle* elementStyle, const StyleKeyframe* keyframe, KeyframeValue& keyframeValue)
@@ -1194,6 +1192,7 @@ void StyleResolver::keyframeStylesForAnimation(Element* e, const RenderStyle* el
         keyframeValue.setStyle(styleForKeyframe(elementStyle, hundredPercentKeyframe, keyframeValue));
         list.insert(keyframeValue);
     }
+    m_state.clear();
 }
 
 PassRefPtr<RenderStyle> StyleResolver::pseudoStyleForElement(Element* e, const PseudoStyleRequest& pseudoStyleRequest, RenderStyle* parentStyle)
@@ -1227,8 +1226,10 @@ PassRefPtr<RenderStyle> StyleResolver::pseudoStyleForElement(Element* e, const P
         matchAuthorRules(collector, false);
     }
 
-    if (collector.matchedResult().matchedProperties.isEmpty())
+    if (collector.matchedResult().matchedProperties.isEmpty()) {
+        state.clear();

[Jeffrey Yasskin, 2013/07/11 21:24:05]

This .clear() on an early return is a good sign that we want an RAII/scoped
object instead of explicit clear()s, but some of the other uses make that
tricky. The scope would likely start at an initForStyleResolve() call and would
auto-clear the state.

         return 0;
+    }
 
     state.style()->setStyleType(pseudoStyleRequest.pseudoId);
 
@@ -1243,7 +1244,7 @@ PassRefPtr<RenderStyle> StyleResolver::pseudoStyleForElement(Element* e, const P
     document()->didAccessStyleResolver();
 
     // Now return the style.
-    return state.takeStyle();
+    return state.takeStyleAndClear();
 }
 
 PassRefPtr<RenderStyle> StyleResolver::styleForPage(int pageIndex)
@@ -1283,7 +1284,7 @@ PassRefPtr<RenderStyle> StyleResolver::styleForPage(int pageIndex)
     document()->didAccessStyleResolver();
 
     // Now return the style.
-    return m_state.takeStyle();
+    return m_state.takeStyleAndClear();
 }
 
 PassRefPtr<RenderStyle> StyleResolver::defaultStyleForElement()
@@ -1726,6 +1727,7 @@ PassRefPtr<CSSRuleList> StyleResolver::pseudoStyleRulesForElement(Element* e, Ps
         matchAuthorRules(collector, rulesToInclude & EmptyCSSRules);
     }
 
+    m_state.clear();
     return collector.matchedRuleList();
 }
 
@@ -2054,6 +2056,7 @@ void StyleResolver::applyPropertyToStyle(CSSPropertyID id, CSSValue* value, Rend
     m_state.initForStyleResolve(document(), 0, style);
     m_state.setStyle(style);
     applyPropertyToCurrentStyle(id, value);
+    m_state.clear();
 }
 
 void StyleResolver::applyPropertyToCurrentStyle(CSSPropertyID id, CSSValue* value)