Change the visual appearance of panel on GTK per new UI design.

chrome/browser/ui/panels/native_panel.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_PANELS_NATIVE_PANEL_H_
 #define CHROME_BROWSER_UI_PANELS_NATIVE_PANEL_H_
 #pragma once
 
 #include "chrome/browser/ui/panels/panel.h"
 #include "ui/gfx/native_widget_types.h"
@@ skipping 83 matching lines @@
   virtual void EnableResizeByMouse(bool enable) = 0;
 
   // Updates the visibility of the minimize and restore buttons.
   virtual void UpdatePanelMinimizeRestoreButtonVisibility() = 0;
 };
 
 // A NativePanel utility interface used for accessing elements of the
 // native panel used only by test automation.
 class NativePanelTesting {
  public:
-  enum TitlebarButtonType {
-    CLOSE_BUTTON,
-    MINIMIZE_BUTTON,
-    RESTORE_BUTTON
-  };
-
   static NativePanelTesting* Create(NativePanel* native_panel);
   virtual ~NativePanelTesting() {}
 
   // Wrappers for the common cases when no modifier is needed.
   void PressLeftMouseButtonTitlebar(const gfx::Point& mouse_location) {
     PressLeftMouseButtonTitlebar(mouse_location, panel::NO_MODIFIER);
   }
   void ReleaseMouseButtonTitlebar() {
     ReleaseMouseButtonTitlebar(panel::NO_MODIFIER);
   }
 
   // |mouse_location| is in screen coordinates.
   virtual void PressLeftMouseButtonTitlebar(
       const gfx::Point& mouse_location, panel::ClickModifier modifier) = 0;
   virtual void ReleaseMouseButtonTitlebar(panel::ClickModifier modifier) = 0;
   virtual void DragTitlebar(const gfx::Point& mouse_location) = 0;
   virtual void CancelDragTitlebar() = 0;
   virtual void FinishDragTitlebar() = 0;
 
   // Verifies, on a deepest possible level, if the Panel is showing the "Draw
   // Attention" effects to the user. May include checking colors etc.
   virtual bool VerifyDrawingAttention() const = 0;
   // Verifies, on a deepest possible level, if the native panel is really
   // active, i.e. the titlebar is painted per its active state.
   virtual bool VerifyActiveState(bool is_active) = 0;
   virtual void WaitForWindowCreationToComplete() const { }
 
   virtual bool IsWindowSizeKnown() const = 0;
   virtual bool IsAnimatingBounds() const = 0;
-  virtual bool IsButtonVisible(TitlebarButtonType button_type) const = 0;
+  virtual bool IsButtonVisible(panel::TitlebarButtonType button_type) const = 0;
 };
 
 #endif  // CHROME_BROWSER_UI_PANELS_NATIVE_PANEL_H_