Camera: Add preview callback surface support

- Add call to set a preview callback surface
- Implement support for HAL2/3 devices
- Still need HAL1 implementation

Change-Id: I0dc0bd72e43d871aa487858d1665c1efca633ffe
diff --git a/services/camera/libcameraservice/Camera2Client.h b/services/camera/libcameraservice/Camera2Client.h
index 713fab3..46c6ceb 100644
--- a/services/camera/libcameraservice/Camera2Client.h
+++ b/services/camera/libcameraservice/Camera2Client.h
@@ -51,6 +51,9 @@
     virtual status_t        setPreviewTexture(
         const sp<IGraphicBufferProducer>& bufferProducer);
     virtual void            setPreviewCallbackFlag(int flag);
+    virtual status_t        setPreviewCallbackTarget(
+        const sp<IGraphicBufferProducer>& callbackProducer);
+
     virtual status_t        startPreview();
     virtual void            stopPreview();
     virtual bool            previewEnabled();