RFR: 6245410: javax.swing.text.html.CSS.Attribute: BACKGROUND_POSITION is not w3c spec compliant [v2]

[Prasanta Sadhukhan]

> [CSS spec for background-position](https://www.w3.org/TR/CSS22/colors.html#propdef-background-position)
> mention the initial value should be "0% 0%" but JDK has the value as "null".
> Rectified the spec violation. 
> No regression is seen in client tests..

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

  Review comment updated

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13114/files
  - new: https://git.openjdk.org/jdk/pull/13114/files/38c0f1a4..1d3948f0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13114&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13114&range=00-01

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/13114.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13114/head:pull/13114

PR: https://git.openjdk.org/jdk/pull/13114