Refactoring: Extract StyleSheetCandidate from DocumentStyleSheetCollection

Source/core/dom/StyleEngine.h

Index: Source/core/dom/StyleEngine.h
diff --git a/Source/core/dom/StyleEngine.h b/Source/core/dom/StyleEngine.h
index 042fa1b11471941871c3fe9ed65243abe7255fbf..7b51f507daf1e3d2a3cc206e2657f9d53589fbe6 100644
--- a/Source/core/dom/StyleEngine.h
+++ b/Source/core/dom/StyleEngine.h
@@ -116,6 +116,12 @@ public:
     void setPreferredStylesheetSetName(const String& name) { m_preferredStylesheetSetName = name; }
     void setSelectedStylesheetSetName(const String& name) { m_selectedStylesheetSetName = name; }
 
+    void selectStylesheetSetName(const String& name)
+    {
+        setPreferredStylesheetSetName(name);
+        setSelectedStylesheetSetName(name);
+    }
+
     void addPendingSheet();
     enum RemovePendingSheetNotificationType {
         RemovePendingSheetNotifyImmediately,