RFR: WIP: 8260528: Clean glass-gtk sizing and positioning code

[Thiago Milczarek Sayao]

On Sun, 14 Feb 2021 22:06:34 GMT, Thiago Milczarek Sayao <tsayao at openjdk.org> wrote:

>> It's been pointed out about this
>> https://stackoverflow.com/questions/49512491/javafx-getting-single-resize-events
>> 
>> My tests point out that this PR causes less sizing events that the current master branch, but I also think this could be improved further.
>> 
>> But, by the nature of X and window managers, window sizes does not account decoration frames, but javafx does (probably mimicking windows behavior). Given this information I probably could reduce further the sizing events, but not make it equivalent to windows.
>
> Changed to WIP to reduce sizing events.

Current Status:

![image](https://user-images.githubusercontent.com/30704286/108422319-2aa0e800-7215-11eb-8b9e-8f62e7f8d553.png)

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PR: https://git.openjdk.java.net/jfx/pull/367