[polari] mainWindow: Work around a warning with recent GTK+

[Florian Müllner <fmuellner src gnome org>]

commit 07c11448f686e33369587551a696848f16af2015
Author: Florian Müllner <fmuellner gnome org>
Date:   Thu Oct 29 14:23:49 2015 +0100

    mainWindow: Work around a warning with recent GTK+
    
    Changing a widget's size request during the parent's allocation is
    evil, and GTK+ (rightfully) started to complain - make the hack
    slightly less evil by passing control back to the mainloop first.

 src/mainWindow.js |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/src/mainWindow.js b/src/mainWindow.js
index c3f3c40..e6b8327 100644
--- a/src/mainWindow.js
+++ b/src/mainWindow.js
@@ -197,7 +197,11 @@ const MainWindow = new Lang.Class({
         // Make sure user-list button is at least as wide as icon buttons
         this._joinMenuButton.connect('size-allocate', Lang.bind(this,
             function(w, rect) {
-                this._showUserListButton.width_request = rect.width;
+                let width = rect.width;
+                Mainloop.idle_add(Lang.bind(this, function() {
+                    this._showUserListButton.width_request = width;
+                    return GLib.SOURCE_REMOVE;
+                }));
             }));
 
         let scroll = builder.get_object('room_list_scrollview');