<Swing Dev> RFR: 4916923: In MetalRootPaneUI, MetalRootLayout does not correctly calculate minimumsize

[Prasanta Sadhukhan]

Please review a fix for an issue where minimumLayoutSize and preferredlayoutSize of MetalRootLayout class wrongly uses
the width of the title pane in the height calculation: Proposed fix is to rectify the anomaly and use tpHeight for
height calculation.

All closed, open jtreg and JCK tests and SwingSet2 Metal L&F are unaffected by this change.

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Commit messages:
 - 4916923: In MetalRootPaneUI, MetalRootLayout does not correctly calculate minimumsize

Changes: https://git.openjdk.java.net/jdk/pull/433/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=433&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-4916923
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/433.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/433/head:pull/433

PR: https://git.openjdk.java.net/jdk/pull/433