Code: static double calcerr(PNG_CONST png_modifier *pm, int in_depth, int out_depth)
 {
    /* Error in the linear composition arithmetic - only relevant when
     * composition actually happens (0 < alpha < 1).
    */
 if ((pm->calculations_use_input_precision ? in_depth : out_depth) == 16)
 return pm->maxcalc16;
 else if (pm->assume_16_bit_calculations)
 return pm->maxcalcG;
 else

       return pm->maxcalc8;
 }

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)
