Refactoring: Introduce HTMLImport interface to form import tree.

Source/core/dom/Document.h

Index: Source/core/dom/Document.h
diff --git a/Source/core/dom/Document.h b/Source/core/dom/Document.h
index cb4d0b6729c976483468a7331e8f5defc0fc4469..0bb0f738ed8946865969adf50b53b00d62af9c7d 100644
--- a/Source/core/dom/Document.h
+++ b/Source/core/dom/Document.h
@@ -102,7 +102,7 @@ class HTMLDocument;
 class HTMLElement;
 class HTMLFrameOwnerElement;
 class HTMLHeadElement;
-class HTMLImportsController;
+class HTMLImport;
 class HTMLIFrameElement;
 class HTMLMapElement;
 class HTMLNameCollection;
@@ -988,8 +988,8 @@ public:
     CustomElementRegistry* registry() const { return m_registry.get(); }
     CustomElementRegistry* ensureCustomElementRegistry();
 
-    void setImports(PassRefPtr<HTMLImportsController>);
-    HTMLImportsController* imports() const { return m_imports.get(); }
+    void setImports(HTMLImport*);
+    HTMLImport* imports() const { return m_imports; }
     bool haveImportsLoaded() const;
     void didLoadAllImports();
 
@@ -1320,7 +1320,7 @@ private:
     OwnPtr<TextAutosizer> m_textAutosizer;
 
     RefPtr<CustomElementRegistry> m_registry;
-    RefPtr<HTMLImportsController> m_imports;
+    HTMLImport* m_imports;
 
     bool m_scheduledTasksAreSuspended;