RFR: 6852577: Only for Nimbus LAF UIManager.get("PasswordField.echoChar") is null

[Prasanta Sadhukhan]

Default echo character obtained through `PasswordField.echoChar` UIProperty returns null for Nimbus L&F,
which is fixed by adding the default character * in the UIDefault table.

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Commit messages:
 - Fix
 - Fix
 - 6852577: Only for Nimbus LAF UIManager.get(PasswordField.echoChar) is null
 - 6852577: Only for Nimbus LAF UIManager.get(PasswordField.echoChar) is null

Changes: https://git.openjdk.org/jdk/pull/10035/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10035&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-6852577
  Stats: 62 lines in 2 files changed: 62 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10035.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10035/head:pull/10035

PR: https://git.openjdk.org/jdk/pull/10035