Add wxWebView::GetNativeBackend() method.

This allows to use platform-specific methods in user code.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72210 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/webview_webkit.h

@@ -111,6 +111,8 @@ public:
     //Virtual Filesystem Support
     virtual void RegisterHandler(wxSharedPtr<wxWebViewHandler> handler);
 
+    virtual void* GetNativeBackend() const { return m_webView; }
+
     // ---- methods not from the parent (common) interface
     bool  CanGetPageSource() const;