C++: prevent cloning the QTextDocument on the UI thread.

Now the document contents (the text) is passed to the background thread,
which in turn will recreate the text document.

Change-Id: I7af47348fe162b53b8b440f1561a9919bf3c381a
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

src/plugins/texteditor/codeassist/runner.cpp

@@ -60,6 +60,7 @@ void ProcessorRunner::setProcessor(IAssistProcessor *computer)
 
 void ProcessorRunner::run()
 {
+    m_interface->recreateTextDocument();
     m_proposal = m_processor->perform(m_interface);
 }