QmlDesigner: reactivate special NavigatorTreeView style

it was a regression when everything switched to fusion style

Change-Id: I87a660afd268ed76608edad8edc93f29db243748
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@theqtcompany.com>

src/plugins/qmldesigner/components/navigator/navigatortreeview.cpp

@@ -41,6 +41,7 @@
 #include <QPixmapCache>
 #include <QMouseEvent>
 #include <QPainter>
+#include <QStyleFactory>
 
 
 namespace QmlDesigner {
@@ -53,6 +54,12 @@ namespace {
 class TreeViewStyle : public QProxyStyle
 {
 public:
+    TreeViewStyle(QObject *parent) : QProxyStyle(QStyleFactory::create("fusion"))
+    {
+        setParent(parent);
+        baseStyle()->setParent(parent);
+    }
+
     void drawPrimitive(PrimitiveElement element, const QStyleOption *option, QPainter *painter, const QWidget *widget = 0) const
     {
         static QRect mouseOverStateSavedFrameRectangle;
@@ -162,9 +169,7 @@ private: // variables
 NavigatorTreeView::NavigatorTreeView(QWidget *parent)
     : QTreeView(parent)
 {
-    TreeViewStyle *style = new TreeViewStyle;
-    setStyle(style);
-    style->setParent(this);
+    setStyle(new TreeViewStyle(this));
 }
 
 void NavigatorTreeView::drawSelectionBackground(QPainter *painter, const QStyleOption &option)

src/plugins/qmldesigner/components/navigator/navigatorwidget.cpp

@@ -36,8 +36,6 @@
 #include <QtDebug>
 #include <utils/fileutils.h>
 
-#include <QStyleFactory>
-
 namespace QmlDesigner {
 
 NavigatorWidget::NavigatorWidget(NavigatorView *view) :
@@ -53,9 +51,6 @@ NavigatorWidget::NavigatorWidget(NavigatorView *view) :
     m_treeView->setDefaultDropAction(Qt::LinkAction);
     m_treeView->setHeaderHidden(true);
 
-    QStyle *style = QStyleFactory::create("fusion");
-    m_treeView->setStyle(style);
-
     QVBoxLayout *layout = new QVBoxLayout;
     layout->setSpacing(0);
     layout->setMargin(0);