Fix for bug 84519 r=adamlock sr=rpotts a=asa. history.go(toofar) gives problems to back/forward buttons

dom/src/base/nsHistory.cpp

@@ -215,11 +215,17 @@ HistoryImpl::GoIndex(PRInt32 aDelta)
   NS_ENSURE_TRUE(webnav, NS_ERROR_FAILURE);
 
   PRInt32 curIndex=-1;
-
-  nsresult rv = session_history->GetIndex(&curIndex);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  return webnav->GotoIndex(curIndex + aDelta);
+  PRInt32 len = 0;
+  nsresult rv = session_history->GetIndex(&curIndex);  
+  rv = session_history->GetCount(&len);
+  
+  PRInt32 index = curIndex + aDelta;
+  if (index > -1  &&  index < len)
+     webnav->GotoIndex(index);
+  // We always want to return a NS_OK, since returning errors 
+  // from GotoIndex() can lead to exceptions and a possible leak
+  // of history length
+  return NS_OK;
 }
 
 NS_IMETHODIMP

xpfe/components/shistory/src/nsSHistory.cpp

@@ -585,8 +585,10 @@ nsSHistory::LoadEntry(PRInt32 aIndex, long aLoadType)
   nsCOMPtr<nsISHEntry> nextEntry;   
   GetEntryAtIndex(mIndex, PR_FALSE, getter_AddRefs(nextEntry));
   nsCOMPtr<nsIHistoryEntry> nHEntry(do_QueryInterface(nextEntry));
-  if (!nextEntry || !prevEntry || !nHEntry)
+  if (!nextEntry || !prevEntry || !nHEntry) {
+    mIndex = oldIndex;
     return NS_ERROR_FAILURE;
+  }
   
   // Send appropriate listener notifications
   PRBool canNavigate = PR_TRUE;
@@ -658,8 +660,12 @@ nsSHistory::LoadEntry(PRInt32 aIndex, long aLoadType)
     }
   
 
-    if (!docShell || !nextEntry || !mRootDocShell)
+  if (!docShell || !nextEntry || !mRootDocShell) {
+     // we did not successfully go to the proper index.
+     // reset mIndex to what it was before returning error
+      mIndex = oldIndex;
       return NS_ERROR_FAILURE;
+  }
 
     /* Set the loadType in the SHEntry too to  what was passed on.
      * This will be passed on to child subframes later in nsDocShell,