RFR: 8236651: Simplify and update glass gtk backend

Wed Jan 13 12:59:54 UTC 2021

On Wed, 1 Apr 2020 03:21:31 GMT, Thiago Milczarek Sayao <tsayao at openjdk.org> wrote:

>> Ubuntu 20.04 Test Results
>> 
>> Updated April 2nd.
>> 
>> ![image](https://user-images.githubusercontent.com/30704286/78299385-28a23d80-750c-11ea-9edd-ac264f16c194.png)
>
> Test on 16.04 (without Webkit - it does not build on 16.04 anymore)
> 
> Updated April 2nd.
> 
> ![image](https://user-images.githubusercontent.com/30704286/78316727-c14db300-7536-11ea-86e9-4d5c56e4d92c.png)
> 
> Note: DatePickerTest works when run alone.

I will keep testing it, but I think it's looking good.

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PR: https://git.openjdk.java.net/jfx/pull/77