Introduce ChildNode IDL interface

Source/core/dom/CharacterData.idl

Index: Source/core/dom/CharacterData.idl
diff --git a/Source/core/dom/CharacterData.idl b/Source/core/dom/CharacterData.idl
index 9d8ee85f7d1404164586cc68f24cdfa6d7803c34..f57eab73094a125a92d268fa4d91475a851882a2 100644
--- a/Source/core/dom/CharacterData.idl
+++ b/Source/core/dom/CharacterData.idl
@@ -36,10 +36,5 @@ interface CharacterData : Node {
      [RaisesException] void replaceData([IsIndex,Default=Undefined] optional unsigned long offset, 
                                     [IsIndex,Default=Undefined] optional unsigned long length,
                                     [Default=Undefined] optional DOMString data);
-
-    // ChildNode interface API
-    readonly attribute Element previousElementSibling;
-    readonly attribute Element nextElementSibling;
-    [RaisesException] void remove();
 };