Fix WebEngineView flashing when closing popup

Closing a popup (eg. HTML select element) might cause WebEngineView to
flash on macOS. This seems to be related to the window's NSPanel
destruction and seems to appear only if the Qt::ToolTip window flag is
set.

Fixes: QTBUG-77072
Fixes: QTBUG-78084
Change-Id: I72af67ee97304278870b312482f8f9058ecd1233
Reviewed-by: Jüri Valdmann <[email protected]>
(cherry picked from commit 2f72083)

Author: stampho

src/webengine/render_widget_host_view_qt_delegate_quickwindow.cpp

@@ -47,7 +47,7 @@ namespace QtWebEngineCore {
 RenderWidgetHostViewQtDelegateQuickWindow::RenderWidgetHostViewQtDelegateQuickWindow(RenderWidgetHostViewQtDelegate *realDelegate)
     : m_realDelegate(realDelegate)
 {
-    setFlags(Qt::ToolTip | Qt::FramelessWindowHint | Qt::WindowDoesNotAcceptFocus);
+    setFlags(Qt::Tool | Qt::FramelessWindowHint | Qt::WindowDoesNotAcceptFocus);
 }
 
 RenderWidgetHostViewQtDelegateQuickWindow::~RenderWidgetHostViewQtDelegateQuickWindow()