QmlDesigner.Rewriter: fixing encoding issue for Qt 4

QString uses utf-16 internally. If we explicitly convert to utf-8
and then use the QByteArray implicit constructor of QString again,
Qt 4 will interpret the utf-8 encoded string as latin1.
This results in a wrong string for everything that is not pure ASCII.

With Qt 5 it works, since the assumed default encoding of QByteArray
is utf-8. Still any conversion does not make sense.

Task-number: QTCREATORBUG-9493
Change-Id: Ifbaa4684e85d0ccd677956eeff88b4cc7d807922
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@digia.com>

src/plugins/qmldesigner/designercore/model/rewriterview.cpp

@@ -569,7 +569,7 @@ void RewriterView::resetToLastCorrectQml()
     m_textModifier->textDocument()->undo();
     m_textModifier->textDocument()->clearUndoRedoStacks(QTextDocument::RedoStack);
     ModelAmender differenceHandler(m_textToModelMerger.data());
-    m_textToModelMerger->load(m_textModifier->text().toUtf8(), differenceHandler);
+    m_textToModelMerger->load(m_textModifier->text(), differenceHandler);
 
     leaveErrorState();
 }
@@ -759,7 +759,7 @@ void RewriterView::qmlTextChanged()
         switch (m_differenceHandling) {
             case Validate: {
                 ModelValidator differenceHandler(m_textToModelMerger.data());
-                if (m_textToModelMerger->load(newQmlText.toUtf8(), differenceHandler))
+                if (m_textToModelMerger->load(newQmlText, differenceHandler))
                     lastCorrectQmlSource = newQmlText;
                 break;
             }