Bug 720311 - Don't open formhistory.sqlite on shutdown in order to close it. r=mak

--HG--
extra : rebase_source : 675477f85954d74601b69fe1ab6f937e50e5adcf

toolkit/components/satchel/nsFormHistory.js

@@ -923,7 +923,10 @@ FormHistory.prototype = {
             stmt.finalize();
         }
         this.dbStmts = {};
-        if (this.dbConnection === undefined)
+
+        let connectionDescriptor = Object.getOwnPropertyDescriptor(FormHistory.prototype, "dbConnection");
+        // Return if the database hasn't been opened.
+        if (!connectionDescriptor || connectionDescriptor.value === undefined)
             return;
 
         let completed = false;