Make down-conversion explicit from CFX_ByteString to CFX_ByteStringC.

xfa/fwl/basewidget/fwl_editimp.cpp

Index: xfa/fwl/basewidget/fwl_editimp.cpp
diff --git a/xfa/fwl/basewidget/fwl_editimp.cpp b/xfa/fwl/basewidget/fwl_editimp.cpp
index 08e44f13ddbf02f352fe44f91b5cfe90c011a709..83869f39e80a4a0cc75ebf2bdc32820466cf6189 100644
--- a/xfa/fwl/basewidget/fwl_editimp.cpp
+++ b/xfa/fwl/basewidget/fwl_editimp.cpp
@@ -734,14 +734,14 @@ FX_BOOL CFWL_EditImp::Undo() {
     return FALSE;
   }
   CFX_ByteString bsRecord = m_RecordArr[m_iCurRecord--];
-  return Undo(bsRecord);
+  return Undo(bsRecord.AsByteStringC());
 }
 FX_BOOL CFWL_EditImp::Redo() {
   if (!CanRedo()) {
     return FALSE;
   }
   CFX_ByteString bsRecord = m_RecordArr[++m_iCurRecord];
-  return Redo(bsRecord);
+  return Redo(bsRecord.AsByteStringC());
 }
 FX_BOOL CFWL_EditImp::CanUndo() {
   return m_iCurRecord >= 0;