AutoTest: Only handle document updates if necessary

Do not send qml document updated unnecessarily in case we know
that nothing had changed at all.

Change-Id: I1d6b94dcd68753e0f451a2812a752ff92f4860af
Reviewed-by: David Schulz <david.schulz@qt.io>
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/plugins/autotest/testcodeparser.h

@@ -97,6 +97,7 @@ private:
     QThreadPool *m_threadPool = nullptr;
     Utils::FutureSynchronizer m_futureSynchronizer;
     std::unique_ptr<Utils::TaskTree> m_taskTree;
+    QHash<Utils::FilePath, int> m_qmlEditorRev;
 };
 
 } // namespace Internal