winrt: Introduce DirectX pipeline bypass.

Qt Windows Runtime camera uses DirectVideo to convert NV12 format
texture to BGRA format texture. As the EGL Node can draw using NV12
already, allow video render control to choose which path to take. By
default use DirectVideo. Bypass can be used as fallback when
DirectVideo cannot be used or is not working.

Task-Id: QTBUG-48331
Change-Id: I0cb87a7c4523bfb60610e6b41ab3fb05aff092a1
Reviewed-by: Andrew Knight <andrew.knight@intopalo.com>

src/plugins/winrt/qwinrtcameravideorenderercontrol.h

@@ -56,6 +56,7 @@ public:
     ~QWinRTCameraVideoRendererControl();
 
     bool render(ID3D11Texture2D *texture) Q_DECL_OVERRIDE;
+    bool dequeueFrame(QVideoFrame *frame) Q_DECL_OVERRIDE;
     void queueBuffer(IMF2DBuffer *buffer);
     void discardBuffers();
     void incrementProbe();