Code:  static size_t safecat(char *buffer, size_t bufsize, size_t pos,
   PNG_CONST char *cat)
 {
    while (pos < bufsize && cat != NULL && *cat != 0)
       buffer[pos++] = *cat++;

 if (pos >= bufsize)
      pos = bufsize-1;

   buffer[pos] = 0;
 return pos;
}

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)
