media: Always define |cdm_id| in CdmContext.

content/renderer/media/crypto/proxy_media_keys.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 "content/renderer/media/crypto/proxy_media_keys.h"
 
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/logging.h"
@@ skipping 122 matching lines @@
     const std::string& web_session_id,
     scoped_ptr<media::SimpleCdmPromise> promise) {
   promise->reject(NOT_SUPPORTED_ERROR, 0, "Not yet implemented.");
 }
 
 media::CdmContext* ProxyMediaKeys::GetCdmContext() {
   return this;
 }
 
 media::Decryptor* ProxyMediaKeys::GetDecryptor() {
-  return NULL;
+  return nullptr;
 }
 
 int ProxyMediaKeys::GetCdmId() const {
   return cdm_id_;
 }
 
 void ProxyMediaKeys::OnSessionCreated(uint32 session_id,
                                       const std::string& web_session_id) {
   AssignWebSessionId(session_id, web_session_id);
   scoped_ptr<media::CdmPromise> promise = TakePromise(session_id);
@@ skipping 127 matching lines @@
 
 scoped_ptr<media::CdmPromise> ProxyMediaKeys::TakePromise(uint32_t session_id) {
   PromiseMap::iterator it = session_id_to_promise_map_.find(session_id);
   // May not be a promise associated with this session for asynchronous events.
   if (it == session_id_to_promise_map_.end())
     return scoped_ptr<media::CdmPromise>();
   return session_id_to_promise_map_.take_and_erase(it);
 }
 
 }  // namespace content