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);
}

Commit Message: DO NOT MERGE Update libpng to 1.6.20

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

CWE ID: 
transform_disable(PNG_CONST char *name)
transform_disable(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);
}
