Code: transform_disable(PNG_CONST char *name)
 {
    image_transform *list = image_transform_first;
 
 while (list != &image_transform_end)
 {
 if (strcmp(list->name, name) == 0)
 {
 list->enable = 0;
 return;
 }

 list = list->list;
 }

   fprintf(stderr, "pngvalid: --transform-disable=%s: unknown transform\n",
      name);
   exit(99);
}

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)
