CppTools: Cancel parsing if editor is closed

The m_parserFuture.cancel() in ~BuiltinEditorDocumentProcessor() did not
cancel anything. Thus, closing a document while the parser was running
led to a blocking UI thread.

Now it cancels at the next include directive it encounters.

Change-Id: I092fddbbd747e0bc95265b6e9b4fcc26b3f76cb3
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/cpptools/baseeditordocumentparser.cpp

@@ -77,9 +77,16 @@ void BaseEditorDocumentParser::setConfiguration(const Configuration &configurati
 }
 
 void BaseEditorDocumentParser::update(const WorkingCopy &workingCopy)
+{
+    QFutureInterface<void> dummy;
+    update(dummy, workingCopy);
+}
+
+void BaseEditorDocumentParser::update(const QFutureInterface<void> &future,
+                                      const WorkingCopy &workingCopy)
 {
     QMutexLocker locker(&m_updateIsRunning);
-    updateHelper(workingCopy);
+    updateHelper(future, workingCopy);
 }
 
 BaseEditorDocumentParser::State BaseEditorDocumentParser::state() const