Add FakeClipboard implementation for unit tests.

ui/base/clipboard/clipboard_aurax11.cc

 // 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.
 
 #include "ui/base/clipboard/clipboard_aurax11.h"
 
 #include <X11/extensions/Xfixes.h>
 #include <X11/Xatom.h>
 #include <list>
 #include <set>
@@ skipping 652 matching lines @@
 ClipboardAuraX11::ClipboardAuraX11() : aurax11_details_(new AuraX11Details) {
   DCHECK(CalledOnValidThread());
 }
 
 ClipboardAuraX11::~ClipboardAuraX11() {
   DCHECK(CalledOnValidThread());
 
   aurax11_details_->StoreCopyPasteDataAndWait();
 }
 
-uint64 ClipboardAuraX11::GetSequenceNumber(ClipboardType type) {
+uint64 ClipboardAuraX11::GetSequenceNumber(ClipboardType type) const {
   DCHECK(CalledOnValidThread());
   if (type == CLIPBOARD_TYPE_COPY_PASTE)
     return SelectionChangeObserver::GetInstance()->clipboard_sequence_number();
   else
     return SelectionChangeObserver::GetInstance()->primary_sequence_number();
 }
 
 bool ClipboardAuraX11::IsFormatAvailable(const FormatType& format,
                                          ClipboardType type) const {
   DCHECK(CalledOnValidThread());
@@ skipping 245 matching lines @@
   if (format.Equals(GetBitmapFormatType()))
     return;
 
   std::vector<unsigned char> bytes(data_data, data_data + data_len);
   scoped_refptr<base::RefCountedMemory> mem(
       base::RefCountedBytes::TakeVector(&bytes));
   aurax11_details_->InsertMapping(format.ToString(), mem);
 }
 
 }  // namespace ui