Remove obsolete chromeos specific code

ui/base/gtk/tooltip_window_gtk.h

-// Copyright (c) 2011 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 UI_BASE_GTK_TOOLTIP_WINDOW_GTK_H_
-#define UI_BASE_GTK_TOOLTIP_WINDOW_GTK_H_
-#pragma once
-
-#include <string>
-
-#include "base/string16.h"
-#include "ui/base/glib/glib_integers.h"
-#include "ui/base/gtk/gtk_signal.h"
-#include "ui/base/ui_export.h"
-
-typedef struct _GdkEventExpose GdkEventExpose;
-typedef struct _GtkLabel GtkLabel;
-typedef struct _GtkWidget GtkWidget;
-typedef struct _GtkStyle GtkStyle;
-
-namespace ui {
-
-// TooltipWindowGtk provides a customized tooltip window and gives us a
-// chance to apply RGBA colormap on it. This enables the GTK theme engine to
-// draw tooltip with nice shadow and rounded corner on ChromeOS.
-class UI_EXPORT TooltipWindowGtk {
- public:
-  explicit TooltipWindowGtk(GtkWidget* widget);
-  ~TooltipWindowGtk();
-
-  // Sets tooltip text to display.
-  void SetTooltipText(const string16& text);
-
-  GtkLabel* label();
-
- protected:
-  CHROMEGTK_CALLBACK_1(TooltipWindowGtk, gboolean, OnPaint, GdkEventExpose*);
-  CHROMEGTK_CALLBACK_1(TooltipWindowGtk, void, OnStyleSet, GtkStyle*);
-
- private:
-  void Init();
-
-  // Underlying widget of this tooltip window.
-  GtkWidget* host_;
-
-  // GtkWindow of this tooltip window.
-  GtkWidget* window_;
-
-  // The alignment and label widgets contained of the tooltip window.
-  GtkWidget* alignment_;
-  GtkWidget* label_;
-
-  DISALLOW_COPY_AND_ASSIGN(TooltipWindowGtk);
-};
-
-} // namespace ui
-
-#endif  // UI_BASE_GTK_TOOLTIP_WINDOW_GTK_H_