Media Remoting: Add remoting control logic for encrypted contents.

media/remoting/remoting_cdm_context.h

+// Copyright 2016 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 MEDIA_REMOTING_REMOTING_CDM_CONTEXT_H_
+#define MEDIA_REMOTING_REMOTING_CDM_CONTEXT_H_
+
+#include "media/base/cdm_context.h"
+
+namespace media {
+
+class RemotingCdm;
+class RemotingSourceImpl;
+
+// TODO(xjz): Merge this with erickung's implementation.
+class RemotingCdmContext : public CdmContext {
+ public:
+  explicit RemotingCdmContext(RemotingCdm* remoting_cdm);
+  ~RemotingCdmContext() override;
+
+  // If |cdm_context| is an instance of RemotingCdmContext, return a type-casted
+  // pointer to it. Otherwise, return nullptr.
+  static RemotingCdmContext* From(CdmContext* cdm_context);
+
+  RemotingSourceImpl* GetRemotingSource();

[xhwang, 2016/11/05 02:39:58]

based on the discussion, please update this to return a scoped_refptr, since the
caller will take ownership

[xjz, 2016/11/07 19:03:54]

Based on previous discussion (comments), I decide to keep the raw pointer here,
as this method does not mean to transfer the ownership, but get access to the
RemotingSourceImpl. Although the return value is stored in another
scoped_refptr, this RemotingCdmContext still owns this RemotingSourceImpl. 

[xhwang, 2016/11/08 17:39:20]

When the returned value is stored in another scoped_refptr, the caller is a
shared owner. If the caller doesn't need to take the shared ownership, it should
just keep using the raw pointer. In other words, you should pretty much never
wrap a raw pointer of a ref-counted object into a scoped_refptr after creation
time.

+
+  // CdmContext implementations.
+  Decryptor* GetDecryptor() override;
+  int GetCdmId() const override;
+  void* GetClassIdentifier() const override;
+
+ private:
+  RemotingCdm* const remoting_cdm_;  // Outlives this class.
+
+  DISALLOW_COPY_AND_ASSIGN(RemotingCdmContext);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_REMOTING_REMOTING_CDM_CONTEXT_H_