Oilpan: Reapply: Remove all the RefPtrs and most of the raw pointers to style

Source/core/dom/ShadowTreeStyleSheetCollection.h

Index: Source/core/dom/ShadowTreeStyleSheetCollection.h
diff --git a/Source/core/dom/ShadowTreeStyleSheetCollection.h b/Source/core/dom/ShadowTreeStyleSheetCollection.h
index 25323d4e52264b549b0e348a7a4a60a0e7d94f4a..4639325fc05164956dc0b1aad4ad53d18738fd4e 100644
--- a/Source/core/dom/ShadowTreeStyleSheetCollection.h
+++ b/Source/core/dom/ShadowTreeStyleSheetCollection.h
@@ -39,12 +39,18 @@ class StyleSheetCollection;
 class StyleEngine;
 
 class ShadowTreeStyleSheetCollection FINAL : public TreeScopeStyleSheetCollection {
-    WTF_MAKE_NONCOPYABLE(ShadowTreeStyleSheetCollection); WTF_MAKE_FAST_ALLOCATED;
+    WTF_MAKE_NONCOPYABLE(ShadowTreeStyleSheetCollection);
+    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
 public:
     explicit ShadowTreeStyleSheetCollection(ShadowRoot&);
 
     bool updateActiveStyleSheets(StyleEngine*, StyleResolverUpdateMode);
 
+    virtual void trace(Visitor* visitor) OVERRIDE
+    {
+        TreeScopeStyleSheetCollection::trace(visitor);
+    }
+
 private:
     void collectStyleSheets(StyleEngine*, StyleSheetCollection&);
 };