diff --git a/mozilla/layout/base/public/nsIStyleContext.h b/mozilla/layout/base/public/nsIStyleContext.h
index 3e857a859e3..7362701ec82 100644
--- a/mozilla/layout/base/public/nsIStyleContext.h
+++ b/mozilla/layout/base/public/nsIStyleContext.h
@@ -194,15 +194,21 @@ protected:
 #define BORDER_PRECEDENT_LOWER  1
 #define BORDER_PRECEDENT_HIGHER 2
 
+struct nsBorderEdges;
 
 /** an encapsulation of border edge info */
 struct nsBorderEdge
 {
+  /** the thickness of the edge */
   nscoord mWidth;
+  /** the length of the edge */
   nscoord mLength;
   PRUint8 mStyle;  
   nscolor mColor;
+  /** which side does this edge represent? */
   PRUint8 mSide;
+  /** if this edge is an outside edge, the border infor for the adjacent inside object */
+  nsBorderEdges * mInsideNeighbor;
 
   nsBorderEdge();
 };
@@ -214,6 +220,7 @@ inline nsBorderEdge::nsBorderEdge()
   mStyle=NS_STYLE_BORDER_STYLE_NONE;
   mColor=0;
   mSide=NS_SIDE_LEFT;
+  mInsideNeighbor = nsnull;
 };
 
 /** an encapsulation of a border defined by its edges */