Merge StyleSheet into CSSStyleSheet.

sky/engine/core/dom/DocumentStyleSheetCollection.cpp

Index: sky/engine/core/dom/DocumentStyleSheetCollection.cpp
diff --git a/sky/engine/core/dom/DocumentStyleSheetCollection.cpp b/sky/engine/core/dom/DocumentStyleSheetCollection.cpp
index 2e18aa0afe22cf82a0b36b90d1970d459c4d0272..047dba27cd020782bd35d2a0f6a7f1b56a928dbe 100644
--- a/sky/engine/core/dom/DocumentStyleSheetCollection.cpp
+++ b/sky/engine/core/dom/DocumentStyleSheetCollection.cpp
@@ -50,13 +50,13 @@ void DocumentStyleSheetCollection::collectStyleSheetsFromCandidates(StyleEngine*
         Node* n = *it;
         StyleSheetCandidate candidate(*n);
 
-        StyleSheet* sheet = candidate.sheet();
+        CSSStyleSheet* sheet = candidate.sheet();
         if (!sheet)
             continue;
 
         collector.appendSheetForList(sheet);
         if (candidate.canBeActivated())
-            collector.appendActiveStyleSheet(toCSSStyleSheet(sheet));
+            collector.appendActiveStyleSheet(sheet);
     }
 }