RFR: 8274932: Render scales in EmbeddedWindow are not properly updated [v2]

[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 incrementally with two additional commits since the last revision:

 - Set stage scale in FX thread
 - Set stage scale in FX thread

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1171/files
  - new: https://git.openjdk.org/jfx/pull/1171/files/14610e82..24d9272d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1171&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1171&range=00-01

  Stats: 6 lines in 1 file changed: 2 ins; 0 del; 4 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