[perl-Gtk3] Fix a test failure in t/zz-GdkEvent.t

[Torsten Schönfeld <tsch src gnome org>]

commit fd1057d12dc45c7fd93b4969e261cfd46195f1c1
Author: Torsten Schönfeld <kaffeetisch gmx de>
Date:   Mon Apr 3 15:05:16 2017 +0200

    Fix a test failure in t/zz-GdkEvent.t
    
    Apparently, the default main loop's event queue might sometimes already
    contain events even though we did not put any in there (for example, a
    settings change notification).  This caused test failures.  To avoid
    this, clear the event queue before relying on its contents.

 t/zz-GdkEvent.t |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/t/zz-GdkEvent.t b/t/zz-GdkEvent.t
index 859a43b..c146df7 100644
--- a/t/zz-GdkEvent.t
+++ b/t/zz-GdkEvent.t
@@ -397,8 +397,11 @@ SKIP: {
   skip 'misc. stuff; missing annotations', 4
     unless Gtk3::CHECK_VERSION(3, 2, 0);
 
-  my $event = Gtk3::Gdk::Event->new ('button-press');
+  # First, clear all pending events.
+  Gtk3::main_iteration while Gtk3::events_pending;
 
+  # Then add our own.
+  my $event = Gtk3::Gdk::Event->new ('button-press');
   $event->put;
   ok (Gtk3::Gdk::events_pending);
   isa_ok (Gtk3::Gdk::Event::get (), 'Gtk3::Gdk::EventButton');