Back up content.xml when migrating database

Change-Id: I4eacbf689989d20142c04dc8fe586d0054c46350
Reviewed-on: https://gerrit.libreoffice.org/55962
Tested-by: Jenkins
Reviewed-by: Tamás Bunth <btomi96@gmail.com>

dbaccess/source/core/dataaccess/datasource.cxx

@@ -596,7 +596,14 @@ Reference< XConnection > ODatabaseSource::buildLowLevelConnection(const OUString
             bNeedMigration = aWarnDlg.run() == RET_OK;
         }
         if (bNeedMigration)
+        {
+            // back up content xml file if migration was successfull
+            Reference<XStorage> xRootStorage = m_pImpl->getOrCreateRootStorage();
+            xRootStorage->copyElementTo("content.xml", xRootStorage,
+                    "content_before_migration.xml");
+
             m_pImpl->m_sConnectURL = "sdbc:embedded:firebird";
+        }
     }
 #endif