On Linux, the App Launcher is now shown in the taskbar.

ui/views/widget/desktop_aura/desktop_root_window_host_x11.cc

Index: ui/views/widget/desktop_aura/desktop_root_window_host_x11.cc
diff --git a/ui/views/widget/desktop_aura/desktop_root_window_host_x11.cc b/ui/views/widget/desktop_aura/desktop_root_window_host_x11.cc
index b4541d0600f64b558a314e98453fc26f2c3dfdb3..431ba323154923f8f62724b3fda8cbc9195006bc 100644
--- a/ui/views/widget/desktop_aura/desktop_root_window_host_x11.cc
+++ b/ui/views/widget/desktop_aura/desktop_root_window_host_x11.cc
@@ -1014,9 +1014,10 @@ void DesktopRootWindowHostX11::InitX11Window(
   // List of window state properties (_NET_WM_STATE) to set, if any.
   std::vector< ::Atom> state_atom_list;
 
-  // Remove popup windows from taskbar.
-  if (params.type == Widget::InitParams::TYPE_POPUP ||
-      params.type == Widget::InitParams::TYPE_BUBBLE) {
+  // Remove popup windows from taskbar unless overridden.
+  if ((params.type == Widget::InitParams::TYPE_POPUP ||
+       params.type == Widget::InitParams::TYPE_BUBBLE) &&
+      !params.override_show_in_taskbar) {
     state_atom_list.push_back(
         atom_cache_.GetAtom("_NET_WM_STATE_SKIP_TASKBAR"));
   }