RFR: 8274932: Render scales in EmbeddedWindow are not properly updated [v6]

[Prasanta Sadhukhan]

> When the JavaFX scene is set before it is really shown, then the scale factors are not properly propagated to the EmbeddedWindow, resulting in showing wrong scales.
> Fix is made to update scales to EmbeddedWindow

Prasanta Sadhukhan has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains seven commits:

 - Merge branch 'master' of https://git.openjdk.org/jfx into JDK-8274932
 - Merge branch 'master' of https://github.com/openjdk/jfx into JDK-8274932
 - Fix to get correct scale in secondary monitor
 - Set stage scale in FX thread
 - Set stage scale in FX thread
 - Set stage scale in FX thread
 - 8274932: Render scales in EmbeddedWindow are not properly updated

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Changes: https://git.openjdk.org/jfx/pull/1171/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1171&range=05
  Stats: 28 lines in 1 file changed: 15 ins; 1 del; 12 mod
  Patch: https://git.openjdk.org/jfx/pull/1171.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1171/head:pull/1171

PR: https://git.openjdk.org/jfx/pull/1171