RFR: 8272870: Add convenience factory methods for border and background [v2]

[Nir Lisker]

> Added convenience factory factory methods for Background and Border.

Nir Lisker has updated the pull request incrementally with one additional commit since the last revision:

  Corrected comment tags

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Changes:
  - all: https://git.openjdk.java.net/jfx/pull/610/files
  - new: https://git.openjdk.java.net/jfx/pull/610/files/33ef548a..bb54859e

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=610&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=610&range=00-01

  Stats: 8 lines in 2 files changed: 2 ins; 3 del; 3 mod
  Patch: https://git.openjdk.java.net/jfx/pull/610.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/610/head:pull/610

PR: https://git.openjdk.java.net/jfx/pull/610