[epiphany] Ensure new tab button is hidden in app mode

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 0f880c700f0ce3ce1b42e1a337c68a879993194c
Author: Jan-Michael Brummer <jan brummer tabos org>
Date:   Fri Jan 11 12:37:51 2019 +0100

    Ensure new tab button is hidden in app mode
    
    Fixes: https://gitlab.gnome.org/GNOME/epiphany/issues/19

 src/ephy-action-bar-start.c | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/src/ephy-action-bar-start.c b/src/ephy-action-bar-start.c
index 3c83174fb..4576cc045 100644
--- a/src/ephy-action-bar-start.c
+++ b/src/ephy-action-bar-start.c
@@ -484,6 +484,10 @@ ephy_action_bar_start_constructed (GObject *object)
   }
   g_signal_connect (action_bar_start->homepage_button, "button-release-event",
                     G_CALLBACK (homepage_button_release_event_cb), action_bar_start);
+
+  /* New Tab Button */
+  if (ephy_embed_shell_get_mode (embed_shell) == EPHY_EMBED_SHELL_MODE_APPLICATION)
+    gtk_widget_set_visible (action_bar_start->new_tab_button, FALSE);
 }
 
 static void