am 5bf786d8: surfaceflinger: recompute visibility after sideband stream change

    if (android_atomic_acquire_cas(true, false, &mSidebandStreamChanged) == 0) {

        // mSidebandStreamChanged was true

        mSidebandStream = mSurfaceFlingerConsumer->getSidebandStream();

        recomputeVisibleRegions = true;

        const State& s(getDrawingState());

        return s.transform.transform(Region(Rect(s.active.w, s.active.h)));

    }

    Region outDirtyRegion;