linux: Remove all the X and GTK+ related implementations.

Now we only uses GTK+ for app indicator and status icon, also notice the
in Chrome35 the Gtk2StatusIcon class doesn't exist yet so we shipp
related files under chromium_src, remember to delete them after upgraded
to Chrome36.

atom/browser/ui/tray_icon_gtk.h

@@ -0,0 +1,43 @@
+// Copyright (c) 2014 GitHub, Inc. All rights reserved.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#ifndef ATOM_BROWSER_UI_TRAY_ICON_GTK_H_
+#define ATOM_BROWSER_UI_TRAY_ICON_GTK_H_
+
+#include <string>
+
+#include "atom/browser/ui/tray_icon.h"
+#include "ui/views/linux_ui/status_icon_linux.h"
+
+namespace views {
+class StatusIconLinux;
+}
+
+namespace atom {
+
+class TrayIconGtk : public TrayIcon,
+                    public views::StatusIconLinux::Delegate {
+ public:
+  TrayIconGtk();
+  virtual ~TrayIconGtk();
+
+  // TrayIcon:
+  virtual void SetImage(const gfx::ImageSkia& image) OVERRIDE;
+  virtual void SetPressedImage(const gfx::ImageSkia& image) OVERRIDE;
+  virtual void SetToolTip(const std::string& tool_tip) OVERRIDE;
+  virtual void SetContextMenu(ui::SimpleMenuModel* menu_model) OVERRIDE;
+
+ private:
+  // views::StatusIconLinux::Delegate:
+  virtual void OnClick() OVERRIDE;
+  virtual bool HasClickAction() OVERRIDE;
+
+  scoped_ptr<views::StatusIconLinux> icon_;
+
+  DISALLOW_COPY_AND_ASSIGN(TrayIconGtk);
+};
+
+}  // namespace atom
+
+#endif  // ATOM_BROWSER_UI_TRAY_ICON_GTK_H_