8362091: Window title bar should reflect scene color scheme

[mstr2]

Currently, the color scheme of a system-decorated stage is as follows:

• On Windows, the title bar is always light (even if the OS color scheme is dark).
• On macOS and Linux, the title bar is light or dark depending on the OS color scheme.

The expected behavior is that the title bar matches the color scheme of the Scene.
If an application doesn't specify a color scheme, the title bar color should match the OS color scheme.

This PR fixes the behavior for Windows and macOS, but not for Linux (there's no good way to do that).
Depending on how you look at it, this is either a bug fix or an enhancement.

/reviewers 2

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Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed (2 reviews required, with at least 1 Reviewer, 1 Author)

Issue

• JDK-8362091: Window title bar should reflect scene color scheme (Enhancement - P4)

Reviewing

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Update a local copy of the PR:
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[bridgekeeper]

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[openjdk]

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[openjdk]

@mstr2
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 2 (with at least 1 Reviewer, 1 Author).

[mlbridge]

Webrevs

• 00: Full (8fa90944)