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

ui/views/widget/desktop_aura/desktop_root_window_host_x11.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/widget/desktop_aura/desktop_root_window_host_x11.h"
 
 #include <X11/extensions/shape.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/Xatom.h>
 #include <X11/Xregion.h>
@@ skipping 996 matching lines @@
                   xwindow_,
                   atom_cache_.GetAtom("_NET_WM_WINDOW_TYPE"),
                   XA_ATOM,
                   32,
                   PropModeReplace,
                   reinterpret_cast<unsigned char*>(&window_type), 1);
 
   // 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.force_show_in_taskbar) {
     state_atom_list.push_back(
         atom_cache_.GetAtom("_NET_WM_STATE_SKIP_TASKBAR"));
   }
 
   // If the window should stay on top of other windows, add the
   // _NET_WM_STATE_ABOVE property.
   is_always_on_top_ = params.keep_on_top;
   if (is_always_on_top_)
     state_atom_list.push_back(atom_cache_.GetAtom("_NET_WM_STATE_ABOVE"));
 
@@ skipping 510 matching lines @@
   if (linux_ui) {
     ui::NativeTheme* native_theme = linux_ui->GetNativeTheme();
     if (native_theme)
       return native_theme;
   }
 
   return ui::NativeTheme::instance();
 }
 
 }  // namespace views