Use current gtk dialogs in linux_aura.

ui/base/linux_ui.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 UI_BASE_LINUX_UI_H_
 #define UI_BASE_LINUX_UI_H_
 
+#include "ui/base/dialogs/select_file_dialog.h"
 #include "ui/base/ui_export.h"
 #include "third_party/skia/include/core/SkColor.h"
 
 // The main entrypoint into Linux toolkit specific code. GTK code should only
 // be executed behind this interface.
 
 namespace gfx {
 class Image;
 }
 
 namespace ui {
+class SelectFilePolicy;
 
 // Adapter class with targets to render like different toolkits. Set by any
 // project that wants to do linux desktop native rendering.
 //
 // TODO(erg): We're hardcoding GTK2, when we'll need to have backends for (at
 // minimum) GTK2 and GTK3. LinuxUI::instance() should actually be a very
 // complex method that pokes around with dlopen against a libuigtk2.so, a
 // liuigtk3.so, etc.
 class UI_EXPORT LinuxUI {
  public:
   virtual ~LinuxUI() {}
 
   // Sets the dynamically loaded singleton that draws the desktop native UI.
   static void SetInstance(LinuxUI* instance);
 
   // Returns a LinuxUI instance for the toolkit used in the user's desktop
   // environment.
   //
   // Can return NULL, in case no toolkit has been set. (For example, if we're
   // running with the "--ash" flag.)
   static const LinuxUI* instance();
 
   // Returns an themed image per theme_provider.h
   virtual bool UseNativeTheme() const = 0;
   virtual gfx::Image* GetThemeImageNamed(int id) const = 0;
   virtual bool GetColor(int id, SkColor* color) const = 0;
+
+  // Returns a native file selection dialog.
+  virtual SelectFileDialog* CreateSelectFileDialog(
+      SelectFileDialog::Listener* listener,
+      SelectFilePolicy* policy) const = 0;
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_LINUX_UI_H_