RFR: 8295327: JavaFX - IllegalArgumentException when printing with margins equal to 0

[Phil Race]

If floating point error caused a small negative value in the conversions needed from ISO to US measurements, then this will cause the IAE reported. 
The code doing the rounding should not have used Math.abs()

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Commit messages:
 - 8295327

Changes: https://git.openjdk.org/jfx/pull/934/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=934&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8295327
  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jfx/pull/934.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/934/head:pull/934

PR: https://git.openjdk.org/jfx/pull/934