[OpenJDK 2D-Dev] [15] RFR JDK-8195841: PNGImageReader.readNullTerminatedString() doesnt check for non-null terminated strings with length equal to maxLen

[Jayathirth D v]

Hello All,

Please review the following fix for JDK 15:

Bug : https://bugs.openjdk.java.net/browse/JDK-8195841 
<https://bugs.openjdk.java.net/browse/JDK-6532025>
Webrev : http://cr.openjdk.java.net/~jdv/8195841/ 
<http://cr.openjdk.java.net/~jdv/8195841/> 

Issue : PNGImageReader doesn’t check null terminated string for keyword when 
its length is maximum length
Solution : After we are done with reading the keyword stream make sure that 
last byte read is NUL.

Thanks,
Jay