[Oilpan]: Make StylePropertySet fully garbage collected.

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 2b7d079b3466524093903e4a6272666440c35774..a0899043b0ea17ecaf0d810a9e5fa02cf7464482 100644
--- a/Source/core/css/resolver/StyleResolver.cpp
+++ b/Source/core/css/resolver/StyleResolver.cpp
@@ -107,7 +107,7 @@ RenderStyle* StyleResolver::s_styleNotYetAvailable;
 
 static StylePropertySet* leftToRightDeclaration()
 {
-    DEFINE_STATIC_REF(MutableStylePropertySet, leftToRightDecl, (MutableStylePropertySet::create()));
+    DEFINE_STATIC_REF_WILL_BE_PERSISTENT(MutableStylePropertySet, leftToRightDecl, (MutableStylePropertySet::create()));
     if (leftToRightDecl->isEmpty())
         leftToRightDecl->setProperty(CSSPropertyDirection, CSSValueLtr);
     return leftToRightDecl;
@@ -115,7 +115,7 @@ static StylePropertySet* leftToRightDeclaration()
 
 static StylePropertySet* rightToLeftDeclaration()
 {
-    DEFINE_STATIC_REF(MutableStylePropertySet, rightToLeftDecl, (MutableStylePropertySet::create()));
+    DEFINE_STATIC_REF_WILL_BE_PERSISTENT(MutableStylePropertySet, rightToLeftDecl, (MutableStylePropertySet::create()));
     if (rightToLeftDecl->isEmpty())
         rightToLeftDecl->setProperty(CSSPropertyDirection, CSSValueRtl);
     return rightToLeftDecl;
@@ -1591,6 +1591,7 @@ bool StyleResolver::mediaQueryAffectedByViewportChange() const
 void StyleResolver::trace(Visitor* visitor)
 {
     visitor->trace(m_keyframesRuleMap);
+    visitor->trace(m_matchedPropertiesCache);
     visitor->trace(m_viewportDependentMediaQueryResults);
     visitor->trace(m_viewportStyleResolver);
     visitor->trace(m_features);