Add Mojo CDM Service.

media/mojo/interfaces/content_decryption_module.mojom

Index: media/mojo/interfaces/content_decryption_module.mojom
diff --git a/media/mojo/interfaces/content_decryption_module.mojom b/media/mojo/interfaces/content_decryption_module.mojom
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+// 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.
+
+module mojo;
+
+import "media/mojo/interfaces/decryptor.mojom";
+
+// Transport layer of media::MediaKeys::Exception (see media/base/media_keys.h).
+// This is used for ContentDecryptionModule (CDM) promise rejections or session

[ddorwin, 2014/12/08 23:46:48]

note: session errors only exist in prefixed.

[xhwang, 2014/12/10 04:59:15]

Done.

+// errors.
+enum CdmException {
+  NOT_SUPPORTED_ERROR,
+  INVALID_STATE_ERROR,
+  INVALID_ACCESS_ERROR,
+  QUOTA_EXCEEDED_ERROR,
+  UNKNOWN_ERROR,
+  CLIENT_ERROR,
+  OUTPUT_ERROR
+};
+
+// Transport layer of media::CdmContext (see media/base/cdm_context.h), which 
+// represents the context that a media pipeline needs from a CDM to decrypt
+// (and decode) encrypted buffers.
+// A CDM implementation must choose to support either an explicit or an implicit

[ddorwin, 2014/12/08 23:46:48]

nit: drop second "an"

[xhwang, 2014/12/10 04:59:15]

Done.

+// decryptor:
+// - Explicit decryptor: non-null |decryptor| and invalid |cdm_id|. The client

[ddorwin, 2014/12/08 23:46:48]

I wonder if this interface should have getters that fail when the wrong one is
called rather than just being null/invalid. Maybe too much for too little,
though.

[xhwang, 2014/12/10 04:59:15]

The current approach seems clean to me. I'll see how this evolves.

+//                       (e.g. media pipeline) will use the |decryptor| directly
+//                       to decrypt (and decode) encrypted buffers.
+// - Implicit decryptor: null |decryptor| and valid |cdm_id|. The client (e.g.
+//                       media pipeline) will use the |cdm_id| to locate a
+//                       decryptor and associate it with the client.
+const int32 kInvalidCdmId = 0;
+struct CdmContext {
+  Decryptor? decryptor;

[ddorwin, 2014/12/08 23:46:48]

How do these things get initialized?

[xhwang, 2014/12/10 04:59:15]

I think they will be initialized to null by default.

+  int32 cdm_id;
+};
+
+// Transport layer of media::CdmPromise (see media/base/cdm_promise.h).
+// - When |success| is true, the promise is resolved and all other fields should

[ddorwin, 2014/12/08 23:46:48]

This is weird. And what about the values we need for success? Can we have a
different callback/client function for failure?

Oh, I guess not since the function is 1:1.

[xhwang, 2014/12/10 04:59:15]

Acknowledged.

+//   be ignored.
+// - When |success| is false, the promise is rejected with |exception_code|,
+//   |system_code| and |error_message|.
+struct CdmPromiseResult {
+  bool success;
+  CdmException exception_code;

[ddorwin, 2014/12/08 23:46:48]

_code is unnecessary?

[xhwang, 2014/12/10 04:59:15]

Done.

+  uint32 system_code;
+  string error_message;
+};
+
+// An interface that represents a CDM in the Encrypted Media Extensions (EME)
+// spec (https://w3c.github.io/encrypted-media/). See media/base/media_keys.h.
+[Client=ContentDecryptionModuleClient]
+interface ContentDecryptionModule {
+  // See media::MediaKeys::SessionType.
+  enum SessionType {
+    TEMPORARY_SESSION,
+    PERSISTENT_SESSION

[ddorwin, 2014/12/08 23:46:48]

See CDM_7 comments.

[xhwang, 2014/12/10 04:59:15]

I 'll update this after MediaKeys interface is updated.

+  };
+
+  // Provides a server certificate to be used to encrypt messages to the
+  // license server.
+  SetServerCertificate(array<uint8> certificate_data)
+      => (CdmPromiseResult result);
+
+  // Creates a session with the |init_data_type|, |init_data| and |session_type|

[ddorwin, 2014/12/08 23:46:48]

nit: s/a/the/ here and below?

[xhwang, 2014/12/10 04:59:15]

For LoadSession, "the" makes sense. For CreateSession, since we are creating "a"
new session, shouldn't "a" makes more sense?

[ddorwin, 2014/12/12 19:25:12]

Acknowledged.

+  // provided. If |result.success| is false, the output |session_id| will be
+  // null.
+  CreateSession(string init_data_type,
+                array<uint8> init_data,
+                SessionType session_type)
+      => (CdmPromiseResult result, string? session_id);
+
+  // Loads a session with the |session_id| provided. If |result.success| is
+  // false, the output |session_id| will be null. 

[ddorwin, 2014/12/08 23:46:48]

There's also the "not found" case, so I think it can be null in either case.
This text could imply it won't be.

[xhwang, 2014/12/10 04:59:15]

Done.

+  LoadSession(string session_id)
+      => (CdmPromiseResult result, string? session_id);
+
+  // Updates a session specified by |session_id| with |response|.
+  UpdateSession(string session_id, array<uint8> response)
+      => (CdmPromiseResult result);
+
+  // Closes the session specified by |session_id|.
+  CloseSession(string session_id) => (CdmPromiseResult result);
+
+  // Removes stored session data associated with the session specified by

[ddorwin, 2014/12/08 23:46:48]

...the _active_... session... ?

It can't just be used like load().

[xhwang, 2014/12/10 04:59:15]

Done.

+  // |session_id|.
+  RemoveSession(string session_id) => (CdmPromiseResult result);
+
+  // Retrieves the key IDs for keys in the session that the CDM knows are
+  // currently usable to decrypt media data. If |result.success| is
+  // false, the |usable_key_ids| will be null.
+  GetUsableKeyIds(string session_id)
+      => (CdmPromiseResult result, array<array<uint8>>? usable_key_ids);
+  
+  // Retrieves the CdmContext associated with this CDM instance.
+  GetCdmContext(CdmContext& cdm_context);
+};
+
+// Session callbacks. See media/base/media_keys.h for details.
+interface ContentDecryptionModuleClient {
+  OnSessionMessage(string session_id, array<uint8> message,
+                   string destination_url);
+
+  OnSessionReady(string session_id);
+
+  OnSessionClosed(string session_id);
+
+  OnSessionError(string session_id, CdmException exception_code,

[ddorwin, 2014/12/08 23:46:48]

ditto on _code

[xhwang, 2014/12/10 04:59:15]

Done.

+                 uint32 system_code, string error_message);
+
+  OnSessionKeysChange(string session_id, bool has_additional_usable_key);
+
+  OnSessionExpirationUpdate(string session_id, int64 new_expiry_time_usec);
+};