[GTK] `SWT.DIALOG_TRIM` calculates wrong size if `~/.swt/trims.prefs` is not cached

[SyntevoAlex]

Describe the bug If ~/.swt/trims.prefs is not cached yet (which more or less means that SWT runs for the first time on machine), dialogs calculate significantly wrong size.

To Reproduce

final Display display = new Display();
final Shell shell = new Shell(display, SWT.DIALOG_TRIM);
shell.setLayout (new GridLayout (1, true));

Label label = new Label(shell, 0);
label.setText(
	"1. Run on Linux\n" +
	"2. Delete file before running:\n" +
	"   ~/.swt/trims.prefs\n" +
	"3. This shell's size will be incorrect\n"
);

Point size = shell.computeSize(SWT.DEFAULT, SWT.DEFAULT, true);
shell.setMinimumSize(size);
shell.setSize(size);
shell.open();

while (!shell.isDisposed()) {
	if (!display.readAndDispatch()) {
		display.sleep();
	}
}

display.dispose();

Screenshots Expected

Actual

Environment:

1. Select the platform(s) on which the behavior is seen:

• • [ ] All OS
• • [ ] Windows
• • [x] Linux
• • [ ] macOS

[SyntevoAlex]

When debugging the snippet, I observed the height of 325px (it can be seen on screenshots above that it's too tall).

I found that the value is composed the following way:

Important values
	[1]   5 = SWT display.trimWidths [TRIM_TITLE_BORDER]
	[2]  28 = SWT display.trimHeights[TRIM_TITLE_BORDER]
	[3]  23 = GTK get_shadow_width().top
	[4]  29 = GTK get_shadow_width().bottom
	[5]  45 = GTK gtk_widget_get_preferred_height (priv->title_box).natural
	[6] 200 = GTK NO_CONTENT_CHILD_NAT
[7] 297 = 200 + 23 + 29 + 45 // [6] + [3] + [4] + [5]
	In 'gtk_window_realize()'
		GTK sets 'gtk_widget_set_allocation()'
[8] 325 = 297 + 28 // [7] + [2]
	In 'Shell.adjustTrim()' called from 'Shell.setVisible()'
		SWT sets 'gtk_widget_set_size_request()'
	297 = gtk_widget_get_allocation()    seen by SWT snippet
	297 = gdk_window_get_frame_extents() seen by SWT snippet
	325 = screen client rect