Bug 308017 - Bidi: up/down-arrow sometimes behave incorrectly after switching keyboard layout. patch from Uri Bernstein <uriber@gmail.com>, r=smontagu, sr=roc.

layout/generic/nsSelection.cpp

@@ -7388,6 +7388,11 @@ nsTypedSelection::SelectionLanguageChange(PRBool aLangRTL)
     else
       shell->SetCaretBidiLevel(levelAfter);
   }
+  
+  // The caret might have moved, so invalidate the desired X position
+  // for future usages of up-arrow or down-arrow
+  mFrameSelection->InvalidateDesiredX();
+  
   return NS_OK;
 }