media: Support creation and SetCdm() for mojo based CDM.

media/mojo/services/mojo_cdm_service_context.h

+// Copyright 2015 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_MOJO_SERVICES_MOJO_CDM_SERVICE_CONTEXT_H_
+#define MEDIA_MOJO_SERVICES_MOJO_CDM_SERVICE_CONTEXT_H_
+
+#include "base/containers/scoped_ptr_hash_map.h"
+#include "base/macros.h"
+#include "media/base/cdm_context.h"
+#include "media/base/media_export.h"
+#include "media/mojo/services/mojo_cdm_service.h"
+
+namespace media {
+
+// A class that creates, owns and manages all MojoCdmService instances.
+class MEDIA_EXPORT MojoCdmServiceContext : public CdmContextProvider {
+ public:
+  MojoCdmServiceContext();
+  ~MojoCdmServiceContext() override;
+
+  // Creates and returns a MojoCdmService for |key_system|, |security_origin|

[ddorwin, 2015/05/15 19:10:07]

"for" doesn't really apply to the last two parameters.

[xhwang, 2015/06/01 21:21:25]

Done.

+  // and |cdm_id|. The returned MojoCdmService is owned by |this|. Returns
+  // nullptr if no MojoCdmService can be created.
+  MojoCdmService* Create(const mojo::String& key_system,
+                         const mojo::String& security_origin,
+                         int32_t cdm_id);
+
+  // CdmContextProvider implementation.
+  CdmContext* GetCdmContext(int32_t cdm_id) override;

[ddorwin, 2015/05/15 19:10:07]

Why wouldn't a caller just get the context from the MojoCdmService?
If there is a use case where the Service is not known, would it make more sense
to get the service based on the ID? (I don't know - just asking.)

[xhwang, 2015/06/01 21:21:25]

The caller (MojoRendererService) needs to find the correct CdmContext given a
CDM ID. This is because media::Renderer only care about CdmContext:

https://code.google.com/p/chromium/codesearch#chromium/src/media/base/rendere...

We could have something like MojoCdmService* GetCdm(cdm_id), then
mojo_cdm_service->GetCdmContext(). But IMHO, MojoRendererService doesn't need to
know MojoCdmService. So a single GetCdmContext() seems better to me.

+
+  // Called when there is a connection error with |service|.
+  void ServiceHadConnectionError(MojoCdmService* service);
+
+ private:
+  // A map between CDM IDs and MojoCdnServices, which owns all MojoCdmServices

[ddorwin, 2015/05/15 19:10:07]

typo: "Cdn"

grammar: ", which" refers to MojoCdnServices. That means MCS owns all of itself.
I think the RHS is referring to the map. Probably make it a separate sentence.

[xhwang, 2015/06/01 21:21:25]

Done.

+  // created.
+  base::ScopedPtrHashMap<int32_t, MojoCdmService> services_;
+
+  DISALLOW_COPY_AND_ASSIGN(MojoCdmServiceContext);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_MOJO_SERVICES_MOJO_CDM_SERVICE_CONTEXT_H_