Make docked panel always on top for Linux

chrome/browser/ui/gtk/panels/panel_gtk.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_GTK_PANELS_PANEL_GTK_H_
 #define CHROME_BROWSER_UI_GTK_PANELS_PANEL_GTK_H_
 
 #include <gtk/gtk.h>
 #include <map>
 
@@ skipping 110 matching lines @@
   void SetBoundsInternal(const gfx::Rect& bounds);
 
   void LoadingAnimationCallback();
 
   // Returns the size of the window frame around the client content area.
   gfx::Size GetNonClientFrameSize() const;
 
   // Invalidate window to force repaint.
   void InvalidateWindow();
 
+  void UpdateWindowAlwaysOnTopState();
+
   // Callback for accelerator activation. |user_data| stores the command id
   // of the matched accelerator.
   static gboolean OnGtkAccelerator(GtkAccelGroup* accel_group,
                                    GObject* acceleratable,
                                    guint keyval,
                                    GdkModifierType modifier,
                                    void* user_data);
 
   CHROMEGTK_CALLBACK_1(PanelGtk, gboolean, OnMainWindowDeleteEvent,
                        GdkEvent*);
@@ skipping 72 matching lines @@
   // The container for the titlebar.
   scoped_ptr<PanelTitlebarGtk> titlebar_;
 
   // Indicates how the window corner should be rendered, rounded or not.
   panel::CornerStyle corner_style_;
 
   DISALLOW_COPY_AND_ASSIGN(PanelGtk);
 };
 
 #endif  // CHROME_BROWSER_UI_GTK_PANELS_PANEL_GTK_H_