Change nsIFrame::PeekOffset back to NS_IMETHOD to fix bustage from bug 300131

layout/generic/nsFrame.cpp

@@ -4216,7 +4216,7 @@ static PRBool IsMovingInFrameDirection(nsIFrame* frame, nsDirection aDirection,
   return aDirection == (isReverseDirection ? eDirPrevious : eDirNext);
 }
 
-nsresult
+NS_IMETHOD
 nsIFrame::PeekOffset(nsPeekOffsetStruct* aPos)
 {
   if (!aPos)

layout/generic/nsIFrame.h

@@ -1335,7 +1335,7 @@ public:
    *  return NS_ERROR_FAILURE
    *  @param aPOS is defined in nsFrameSelection
    */
-  nsresult PeekOffset(nsPeekOffsetStruct *aPos);
+  NS_IMETHOD PeekOffset(nsPeekOffsetStruct *aPos);
 
   /**
    *  called to find the previous/next selectable leaf frame.