Add FakeClipboard implementation for unit tests.

ui/base/clipboard/clipboard_aura.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_aura.h"
 
 #include <list>
 
 #include "base/basictypes.h"
 #include "base/files/file_path.h"
@@ skipping 510 matching lines @@
   DCHECK(CalledOnValidThread());
   // Make sure clipboard is created.
   GetClipboard();
 }
 
 ClipboardAura::~ClipboardAura() {
   DCHECK(CalledOnValidThread());
   DeleteClipboard();
 }
 
-uint64 ClipboardAura::GetSequenceNumber(ClipboardType type) {
+uint64 ClipboardAura::GetSequenceNumber(ClipboardType type) const {
   DCHECK(CalledOnValidThread());
   return GetClipboard()->sequence_number();
 }
 
 bool ClipboardAura::IsFormatAvailable(const FormatType& format,
                                       ClipboardType type) const {
   DCHECK(CalledOnValidThread());
   DCHECK(IsSupportedClipboardType(type));
   AuraClipboard* clipboard = GetClipboard();
   if (GetPlainTextFormatType().Equals(format) ||
@@ skipping 138 matching lines @@
   ClipboardDataBuilder::WriteBitmap(bitmap);
 }
 
 void ClipboardAura::WriteData(const FormatType& format,
                               const char* data_data,
                               size_t data_len) {
   ClipboardDataBuilder::WriteData(format.ToString(), data_data, data_len);
 }
 
 }  // namespace ui