RFR: JDK-8245919: Region#padding property rendering error [v3]

[John Hendrikx]

> Fix bug in CSS caching code that could reset values on unrelated nodes.
> 
> The bug occurs due to a cache entry being constructed incorrectly when the initial node that triggered the cache entry creation has user set values. The calculated values for properties with a user set value were omitted in the cache entry, and other nodes that later share the same entry would incorrectly assume the omitted property was unstyled and were therefore reset to their default values.

John Hendrikx has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Merge branch 'openjdk:master' into feature/css-cache-bug
 - Fix typo
 - Fix bug in CSS caching code that could reset values on unrelated nodes
   
   The bug occurs due to a cache entry being constructed incorrectly when
   the initial node that triggered the cache entry creation has user set
   values. The calculated values for properties with a user set value were
   omitted in the cache entry, and other nodes that later share the same
   entry would incorrectly assume the omitted property was unstyled and
   were therefore reset to their default values.

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1072/files
  - new: https://git.openjdk.org/jfx/pull/1072/files/5c6e5c1f..2bc5a7f7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1072&range=02
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1072&range=01-02

  Stats: 3952 lines in 65 files changed: 2979 ins; 687 del; 286 mod
  Patch: https://git.openjdk.org/jfx/pull/1072.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1072/head:pull/1072

PR: https://git.openjdk.org/jfx/pull/1072