[OpenJDK 2D-Dev] RFR: 8048583: CustomMediaSizeName class matching to standard media is too loose

[Phil Race]

Bug : https://bugs.openjdk.java.net/browse/JDK-8048583
Fix : http://cr.openjdk.java.net/~prr/8048583/

As described in the bug the basic problem is that we associate
a printer defined media with an inappropriate "standard" media.

If there's no standard media that matches to within a fraction,
don't return one.

It is difficult to provide a direct or useful test for this as
knowing if its right requires having a  CUPS printer
which triggers the code and even then this isn't exposed directly.
It bubbles up as somewhat odd margins for the page ..

But hopefully it should be apparent that saying the paper
size matches to a different size is a problem.

Returning null from CustomMediSizeName.getStandardMedia()
is something that already is possible and I did double-check all
the callers seem to be looking for the possibility of null.

-phil.