Delete StyleSheetList and support code.

sky/engine/core/dom/DocumentStyleSheetCollection.h

Index: sky/engine/core/dom/DocumentStyleSheetCollection.h
diff --git a/sky/engine/core/dom/DocumentStyleSheetCollection.h b/sky/engine/core/dom/DocumentStyleSheetCollection.h
index dc25e307f2e462235e81768c28b2fc18f0601d40..50fce86fc6a5646282df805c2820c4430bff7d45 100644
--- a/sky/engine/core/dom/DocumentStyleSheetCollection.h
+++ b/sky/engine/core/dom/DocumentStyleSheetCollection.h
@@ -32,7 +32,6 @@
 
 namespace blink {
 
-class DocumentStyleSheetCollector;
 class StyleEngine;
 class TreeScope;
 
@@ -46,12 +45,12 @@ public:
     }
 
     void updateActiveStyleSheets(StyleEngine*);
-    void collectStyleSheets(StyleEngine*, DocumentStyleSheetCollector&);
 
 private:
     explicit DocumentStyleSheetCollection(TreeScope&);
 
-    void collectStyleSheetsFromCandidates(StyleEngine*, DocumentStyleSheetCollector&);
+    void collectStyleSheets(StyleEngine*, StyleSheetCollection&);
+    void collectStyleSheetsFromCandidates(StyleEngine*, StyleSheetCollection&);
 };
 
 }