RFR: 8274932: Render scales in EmbeddedWindow are not properly updated

[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

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

Commit messages:
 - 8274932: Render scales in EmbeddedWindow are not properly updated

Changes: https://git.openjdk.org/jfx/pull/1171/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1171&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8274932
  Stats: 8 lines in 1 file changed: 8 ins; 0 del; 0 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