Media Remoting: Add remoting control logic for encrypted contents.

media/base/cdm_context.cc

 // Copyright 2014 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 "media/base/cdm_context.h"
 
 namespace media {
 
 const int CdmContext::kInvalidCdmId = 0;
 
 CdmContext::CdmContext() {}
 
 CdmContext::~CdmContext() {}
 
 void IgnoreCdmAttached(bool /* success */) {}
 
+void* CdmContext::GetClassIdentifier() const {
+  return nullptr;
+}
+
 }  // namespace media