RFR: 8305768: Unify WindowContext in glass-gtk [v2]

[Thiago Milczarek Sayao]

> This unifies and organizes WindowContext of the glass-gtk.
> 
> It does not change any behaviour, just reorganizes the code.

Thiago Milczarek Sayao has updated the pull request incrementally with one additional commit since the last revision:

  Unrelated file

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1085/files
  - new: https://git.openjdk.org/jfx/pull/1085/files/b846ed21..102592e6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1085&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1085&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jfx/pull/1085.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1085/head:pull/1085

PR: https://git.openjdk.org/jfx/pull/1085