RFR: 8236651: Simplify and update glass gtk backend

[Tor (torbuntu)]

On Wed, 29 Jul 2020 20:46:16 GMT, Thiago Milczarek Sayao <tsayao at openjdk.org> wrote:

>> Would it be possible and related to add the gtk touch events to this PR as part of the Glass GTK3 update? Or would
>> follow up update PR adding that be more appropriate?
>> Currently linux desktop does not have touch support because of the missing gesture/touch events from gtk3.
>
> @Torbuntu Not to this PR, I don't want to delay it too much. But can be done (I just do not own a touch device
> currently).

Sounds good! I have a few devices I'd be more than excited to test on, and even help add the feature myself if I can
figure it out if time is a big issue?

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