Add context menu handling for OSR mode.
For OSR mode
when use setContextMenuPolicy with Qt::DefaultContextMenuPolicy, the browser will show default native CEF context menu
for any other context menu policy value, the default native CEF context menu will not show
Add context menu handling for OSR mode. For OSR mode when use setContextMenuPolicy with Qt::DefaultContextMenuPolicy, the browser will show default native CEF context menu for any other context menu policy value, the default native CEF context menu will not show