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

Source/core/dom/DocumentStyleSheetCollection.h

Index: Source/core/dom/DocumentStyleSheetCollection.h
diff --git a/Source/core/dom/DocumentStyleSheetCollection.h b/Source/core/dom/DocumentStyleSheetCollection.h
index e277d2472b0327f866e5637b9ccfd6ec7d7a437c..c49c6ec09497c2530a9c3b0b40c83d982c78f931 100644
--- a/Source/core/dom/DocumentStyleSheetCollection.h
+++ b/Source/core/dom/DocumentStyleSheetCollection.h
@@ -39,13 +39,19 @@ class StyleEngine;
 class TreeScope;
 
 class DocumentStyleSheetCollection FINAL : public TreeScopeStyleSheetCollection {
-    WTF_MAKE_NONCOPYABLE(DocumentStyleSheetCollection); WTF_MAKE_FAST_ALLOCATED;
+    WTF_MAKE_NONCOPYABLE(DocumentStyleSheetCollection);
+    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
 public:
     explicit DocumentStyleSheetCollection(TreeScope&);
 
     bool updateActiveStyleSheets(StyleEngine*, StyleResolverUpdateMode);
     void collectStyleSheets(StyleEngine*, DocumentStyleSheetCollector&);
 
+    virtual void trace(Visitor* visitor) OVERRIDE
+    {
+        TreeScopeStyleSheetCollection::trace(visitor);
+    }
+
 private:
     void collectStyleSheetsFromCandidates(StyleEngine*, DocumentStyleSheetCollector&);
 };