RFR: JDK-8315569: Tests for the contract of SkinBase.layoutChildren(..)

Sat Sep 2 13:01:56 UTC 2023

This PR adds a test that verifies the `SkinBase.layoutChildren(..)` method with different scales.
While not explicitly documented, this method will receive the snapped and correctly calculated x, y, width and height values, so that children of the Control can be layouted correctly without requiring to do many more calculations regarding padding.

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Commit messages:
 - JDK-8315569: Tests for the contract of SkinBase.layoutChildren(..)

Changes: https://git.openjdk.org/jfx/pull/1229/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1229&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315569
  Stats: 123 lines in 1 file changed: 123 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1229.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1229/head:pull/1229

PR: https://git.openjdk.org/jfx/pull/1229