Change various helper classes to transition types to get CSSValue entirely onto the gc heap.

Source/core/css/StyleRuleImport.cpp

Index: Source/core/css/StyleRuleImport.cpp
diff --git a/Source/core/css/StyleRuleImport.cpp b/Source/core/css/StyleRuleImport.cpp
index 954c38c57606c25d6165f8a5ccddd06447151f16..fa7d7baca295e1a383fe1367a95622071956a936 100644
--- a/Source/core/css/StyleRuleImport.cpp
+++ b/Source/core/css/StyleRuleImport.cpp
@@ -31,12 +31,12 @@
 
 namespace WebCore {
 
-PassRefPtrWillBeRawPtr<StyleRuleImport> StyleRuleImport::create(const String& href, PassRefPtr<MediaQuerySet> media)
+PassRefPtrWillBeRawPtr<StyleRuleImport> StyleRuleImport::create(const String& href, PassRefPtrWillBeRawPtr<MediaQuerySet> media)
 {
     return adoptRefCountedWillBeRefCountedGarbageCollected(new StyleRuleImport(href, media));
 }
 
-StyleRuleImport::StyleRuleImport(const String& href, PassRefPtr<MediaQuerySet> media)
+StyleRuleImport::StyleRuleImport(const String& href, PassRefPtrWillBeRawPtr<MediaQuerySet> media)
     : StyleRuleBase(Import)
     , m_parentStyleSheet(0)
     , m_styleSheetClient(this)
@@ -60,6 +60,7 @@ StyleRuleImport::~StyleRuleImport()
 void StyleRuleImport::traceAfterDispatch(Visitor* visitor)
 {
     visitor->trace(m_parentStyleSheet);
+    visitor->trace(m_mediaQueries);
     visitor->trace(m_styleSheet);
     StyleRuleBase::traceAfterDispatch(visitor);
 }