aura: Make 'ui' buildable without gtk.

ui/base/dragdrop/os_exchange_data.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_DRAGDROP_OS_EXCHANGE_DATA_H_
 #define UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_H_
 #pragma once
 
 #include "build/build_config.h"
 
 #include <set>
 #include <string>
 
 #if defined(OS_WIN)
 #include <objidl.h>
-#elif !defined(OS_MACOSX)
+#elif defined(TOOLKIT_USES_GTK)
 #include <gtk/gtk.h>
 #endif
 
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/base/dragdrop/download_file_interface.h"
 #include "ui/base/ui_export.h"
 
 class GURL;
@@ skipping 14 matching lines @@
 // NOTE: Support for html and file contents is required by TabContentViewWin.
 // TabContentsViewGtk uses a different class to handle drag support that does
 // not use OSExchangeData. As such, file contents and html support is only
 // compiled on windows.
 class UI_EXPORT OSExchangeData {
  public:
   // CustomFormats are used for non-standard data types. For example, bookmark
   // nodes are written using a CustomFormat.
 #if defined(OS_WIN)
   typedef CLIPFORMAT CustomFormat;
-#elif !defined(OS_MACOSX)
+#elif defined(TOOLKIT_USES_GTK)
   typedef GdkAtom CustomFormat;
+#else
+  typedef void* CustomFormat;
 #endif
 
   // Enumeration of the known formats.
   enum Format {
     STRING         = 1 << 0,
     URL            = 1 << 1,
     FILE_NAME      = 1 << 2,
     PICKLED_DATA   = 1 << 3,
 #if defined(OS_WIN)
     FILE_CONTENTS  = 1 << 4,
@@ skipping 127 matching lines @@
 
   // Provides the actual data.
   scoped_ptr<Provider> provider_;
 
   DISALLOW_COPY_AND_ASSIGN(OSExchangeData);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_H_