Code: image_transform_png_set_scale_16_mod(PNG_CONST image_transform *this,
     image_pixel *that, png_const_structp pp,
    PNG_CONST transform_display *display)
 {
    if (that->bit_depth == 16)
    {
      that->sample_depth = that->bit_depth = 8;
 if (that->red_sBIT > 8) that->red_sBIT = 8;
 if (that->green_sBIT > 8) that->green_sBIT = 8;
 if (that->blue_sBIT > 8) that->blue_sBIT = 8;
 if (that->alpha_sBIT > 8) that->alpha_sBIT = 8;
 }

 this->next->mod(this->next, that, pp, display);
}

Commit Message: DO NOT MERGE Update libpng to 1.6.20

BUG:23265085
Change-Id: I85199805636d771f3597b691b63bc0bf46084833
(cherry picked from commit bbe98b40cda082024b669fa508931042eed18f82)

CWE ID: 
image_transform_png_set_scale_16_mod(PNG_CONST image_transform *this,
image_transform_png_set_scale_16_mod(const image_transform *this,
     image_pixel *that, png_const_structp pp,
    const transform_display *display)
 {
    if (that->bit_depth == 16)
    {
      that->sample_depth = that->bit_depth = 8;
 if (that->red_sBIT > 8) that->red_sBIT = 8;
 if (that->green_sBIT > 8) that->green_sBIT = 8;
 if (that->blue_sBIT > 8) that->blue_sBIT = 8;
 if (that->alpha_sBIT > 8) that->alpha_sBIT = 8;
 }

 this->next->mod(this->next, that, pp, display);
}
