Bug 599978 - Part 3: Asynchronous isVisited checks should use a read-only cloned connection

Finalize the statement so we do not crash in debug builds.
r=orange

toolkit/components/places/src/History.cpp

@@ -1037,7 +1037,11 @@ History::Shutdown()
       dont_AddRef(static_cast<Step*>(mPendingVisits.PopFront()));
   }
 
+  // Clean up our statements and connection.
   if (mReadOnlyDBConn) {
+    if (mIsVisitedStatement) {
+      (void)mIsVisitedStatement->Finalize();
+    }
     (void)mReadOnlyDBConn->AsyncClose(nsnull);
   }
 }

toolkit/components/places/src/History.h

@@ -123,7 +123,7 @@ private:
   /**
    * An asynchronous statement to query if a URI is visited or not.
    *
-   * @note this should only be accessed by GetIsVisistedStatement.
+   * @note this should only be accessed by GetIsVisistedStatement and Shutdown.
    */
   nsCOMPtr<mozIStorageAsyncStatement> mIsVisitedStatement;