Remove more oilpan.

sky/engine/core/html/imports/HTMLImport.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 76 matching lines @@
 //   until all of its children are loaded.
 //   Note that dynamically added import won't block the parser.
 //
 // - An import under loading also blocks imported documents that follow from being created.
 //   This is because an import can include another import that has same URLs of following ones.
 //   In such case, the preceding import should be loaded and following ones should be de-duped.
 //
 
 // The superclass of HTMLImportTreeRoot and HTMLImportChild
 // This represents the import tree data structure.
-class HTMLImport : public DummyBase<HTMLImport>, public TreeNode<HTMLImport> {
+class HTMLImport : public TreeNode<HTMLImport> {
 public:
     enum SyncMode {
         Sync  = 0,
         Async = 1
     };
 
     virtual ~HTMLImport() { }
 
     // FIXME: Consider returning HTMLImportTreeRoot.
     HTMLImport* root();
@@ skipping 29 matching lines @@
 #endif
 
 private:
     HTMLImportState m_state;
     unsigned m_sync : 1;
 };
 
 } // namespace blink
 
 #endif // HTMLImport_h