RFR: 8267554: Support loading stylesheets from data-URIs [v6]

[Michael Strauß]

> This PR extends data URI support to allow stylesheets to be loaded from data URIs.

Michael Strauß has updated the pull request incrementally with one additional commit since the last revision:

  changes per review

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Changes:
  - all: https://git.openjdk.java.net/jfx/pull/536/files
  - new: https://git.openjdk.java.net/jfx/pull/536/files/c734640f..64d72fe3

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=536&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=536&range=04-05

  Stats: 84 lines in 4 files changed: 52 ins; 9 del; 23 mod
  Patch: https://git.openjdk.java.net/jfx/pull/536.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/536/head:pull/536

PR: https://git.openjdk.java.net/jfx/pull/536