include: Define IElementTraversal interface.

include/mshtmdid.h

@@ -1661,6 +1661,13 @@
 #define DISPID_IHTMLELEMENT6_ONWAITING                DISPID_EVPROP_WAITING
 #define DISPID_IHTMLELEMENT6_IE9_HASATTRIBUTES        DISPID_IE9_ELEMENT+29
 
+/* IElementTraversal */
+#define DISPID_IELEMENTTRAVERSAL_FIRSTELEMENTCHILD      DISPID_IE9_ELEMENT+22
+#define DISPID_IELEMENTTRAVERSAL_LASTELEMENTCHILD       DISPID_IE9_ELEMENT+23
+#define DISPID_IELEMENTTRAVERSAL_PREVIOUSELEMENTSIBLING DISPID_IE9_ELEMENT+24
+#define DISPID_IELEMENTTRAVERSAL_NEXTELEMENTSIBLING     DISPID_IE9_ELEMENT+25
+#define DISPID_IELEMENTTRAVERSAL_CHILDELEMENTCOUNT      DISPID_IE9_ELEMENT+26
+
 /* IHTMLGenericElement */
 #define DISPID_IHTMLGENERICELEMENT_RECORDSET       DISPID_GENERIC+1
 #define DISPID_IHTMLGENERICELEMENT_NAMEDRECORDSET  DISPID_GENERIC+2

include/mshtml.idl

@@ -6617,6 +6617,29 @@ interface IHTMLElement6 : IDispatch
     VARIANT_BOOL ie9_hasAttributes()
 
 /*****************************************************************************
+ *    IElementTraversal interface
+ */
+[
+    odl,
+    oleautomation,
+    dual,
+    uuid(30510736-98b5-11cf-bb82-00aa00bdce0b)
+]
+interface IElementTraversal : IDispatch
+{
+    [propget, id(DISPID_IELEMENTTRAVERSAL_FIRSTELEMENTCHILD)]
+    HRESULT firstElementChild([retval, out] IHTMLElement **p);
+    [propget, id(DISPID_IELEMENTTRAVERSAL_LASTELEMENTCHILD)]
+    HRESULT lastElementChild([retval, out] IHTMLElement **p);
+    [propget, id(DISPID_IELEMENTTRAVERSAL_PREVIOUSELEMENTSIBLING)]
+    HRESULT previousElementSibling([retval, out] IHTMLElement **p);
+    [propget, id(DISPID_IELEMENTTRAVERSAL_NEXTELEMENTSIBLING)]
+    HRESULT nextElementSibling([retval, out] IHTMLElement **p);
+    [propget, id(DISPID_IELEMENTTRAVERSAL_CHILDELEMENTCOUNT)]
+    HRESULT childElementCount([retval, out] long *p);
+}
+
+/*****************************************************************************
  *    IElementSelector interface
  */
 [