Code: image_transform_png_set_expand_mod(PNG_CONST image_transform *this,
     image_pixel *that, png_const_structp pp,
    PNG_CONST transform_display *display)
 {
    /* The general expand case depends on what the colour type is: */
    if (that->colour_type == PNG_COLOR_TYPE_PALETTE)
      image_pixel_convert_PLTE(that);
 else if (that->bit_depth < 8) /* grayscale */

       that->sample_depth = that->bit_depth = 8;
 
    if (that->have_tRNS)
      image_pixel_add_alpha(that, &display->this);
 
    this->next->mod(this->next, that, pp, display);
 }

Vulnerability Type: +Priv 
CWE ID: 
Summary: Unspecified vulnerability in libpng before 1.6.20, as used in Android 4.x before 4.4.4, 5.0.x before 5.0.2, 5.1.x before 5.1.1, and 6.x before 2016-07-01, allows attackers to gain privileges via a crafted application, as demonstrated by obtaining Signature or SignatureOrSystem access, aka internal bug 23265085.
Commit Message: DO NOT MERGE Update libpng to 1.6.20

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