Add use_clibpard_aurax11 gyp flag to allow chromeos-chrome to access X11 Clipboard

ui/base/clipboard/clipboard.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_CLIPBOARD_CLIPBOARD_H_
 #define UI_BASE_CLIPBOARD_CLIPBOARD_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 366 matching lines @@
   void SetGtkClipboard(ClipboardType type);
   // Insert a mapping into clipboard_data_.
   void InsertMapping(const char* key, char* data, size_t data_len);
 
   // Find the gtk clipboard for the passed type enum.
   GtkClipboard* LookupBackingClipboard(ClipboardType type) const;
 
   TargetMap* clipboard_data_;
   GtkClipboard* clipboard_;
   GtkClipboard* primary_selection_;
-#elif defined(USE_AURA) && defined(USE_X11) && !defined(OS_CHROMEOS)
+#elif defined(USE_CLIPBOARD_AURAX11)
  private:
   // We keep our implementation details private because otherwise we bring in
   // the X11 headers and break chrome compile.
   class AuraX11Details;
   scoped_ptr<AuraX11Details> aurax11_details_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(Clipboard);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_CLIPBOARD_CLIPBOARD_H_