RFR: 6513512: MetalLookAndFeel.initClassDefaults does not install an entry for MetalMenuBarUI [v3]

[Prasanta Sadhukhan]

> Spec for [MetalLookAndFeel](https://github.com/openjdk/jdk/blob/master/src/java.desktop/share/classes/javax/swing/plaf/metal/MetalLookAndFeel.java#L247)
> says:
> "...MetalLookAndFeel registers an entry for each of the classes
> in the package javax.swing.plaf.metal that are named MetalXXXUI.
> The string XXX is one of Swing's uiClassIDs. For the uiClassIDs
> that do not have a class in metal, the corresponding class in
> javax.swing.plaf.basic is used. For example, metal does not
> have a class named "MetalColorChooserUI", as such,
> javax.swing.plaf.basic.BasicColorChooserUI is used".
> 
> There is class MetalMenuBarUI, but the method populates given defaults table with the value
> "javax.swing.plaf.basic.BasicMenuBarUI".
> 
> Added entry for MetalMenuBarUI..
> CI tests including JCK tests are ok.

Prasanta Sadhukhan has updated the pull request incrementally with one additional commit since the last revision:

  Spec update

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/11646/files
  - new: https://git.openjdk.org/jdk/pull/11646/files/2ea55a0b..71965da8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11646&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11646&range=01-02

  Stats: 5 lines in 1 file changed: 2 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/11646.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11646/head:pull/11646

PR: https://git.openjdk.org/jdk/pull/11646