RFR: 8236651: Simplify and update glass gtk backend

[Pankaj Bansal]

On Wed, 10 Jun 2020 13:11:29 GMT, Thiago Milczarek Sayao <tsayao at openjdk.org> wrote:

>>> I am running a full test using GTK 3 on Ubuntu 20.04 and will publish results. I will later do the same for Oracle
>>> Linux 7.7.
>>> One thing to note is that this new GTK pipeline doesn't run on Ubuntu 16.04. I get the following running any program:
>>> 
>>> ```
>>> $ java -Djavafx.gtk.experimental=true -Djdk.gtk.verbose=true HelloRectangle
>>> checking GTK version 3
>>> trying GTK library libgtk-3.so.0
>>> using GTK library version 3 set libgtk-3.so.0
>>> Glass GTK library to load is glassgtk3_exp
>>> loaded gdk_x11_display_set_window_scale
>>> java: symbol lookup error: /localhome/kcr/javafx/jfx-tmp/jfx/rt/build/sdk/lib/libglassgtk3_exp.so: undefined symbol:
>>> gdk_display_get_n_monitors ```
>> 
>> I have limited GTK compilation to use GTK 3.8 symbols. Will run more tests, but should fix it.
>
> Here is the result on Ubuntu 20.04 with the latest changes:
> 
> ![image](https://user-images.githubusercontent.com/30704286/84271590-abdea180-ab02-11ea-9d2d-dbca39755db0.png)
> 
> Some tests seems intermittent.

I have run the test on OL82 on updated code. Following are the results. I will rerun this on Ubuntu 18.04 and get back
with the results <img width="647" alt="OL82"
src="https://user-images.githubusercontent.com/6153953/84469824-918dfa80-ac9f-11ea-9494-36208798312a.png">

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