Remove virtualized isRoot/isChild from HTMLImport.

Source/core/html/imports/HTMLImportChild.h

Index: Source/core/html/imports/HTMLImportChild.h
diff --git a/Source/core/html/imports/HTMLImportChild.h b/Source/core/html/imports/HTMLImportChild.h
index e1db3da0a62a1ad8abbd724034b12ac6174638ec..ca61e53cec19d76ad6285c556f18c9b2f6cc1ad9 100644
--- a/Source/core/html/imports/HTMLImportChild.h
+++ b/Source/core/html/imports/HTMLImportChild.h
@@ -65,7 +65,6 @@ public:
     WeakPtr<HTMLImportChild> weakPtr() { return m_weakFactory.createWeakPtr(); }
 
     // HTMLImport
-    virtual bool isChild() const OVERRIDE { return true; }
     virtual Document* document() const OVERRIDE;
     virtual bool isDone() const OVERRIDE;
     virtual HTMLImportLoader* loader() const OVERRIDE { return m_loader; }
@@ -100,7 +99,7 @@ private:
 
 inline HTMLImportChild* toHTMLImportChild(HTMLImport* import)
 {
-    ASSERT(!import || import->isChild());
+    ASSERT(!import || !import->isRoot());
     return static_cast<HTMLImportChild*>(import);
 }