media: Add MediaDrmStorage

media/mojo/interfaces/media_drm_storage.mojom

+// Copyright 2017 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 media.mojom;
+
+import "url/mojo/origin.mojom";
+
+// Allows MediaDrmBridge to store and retrieve persistent data. This is needed
+// for features like per-origin provisioning and persistent license support.
+interface MediaDrmStorage {
+  // Initializes |this| to be bound to the |origin|. This should not modify
+  // anything in the storage.
+  Initialize(url.mojom.Origin origin);
+
+  // Saves |origin| in the storage after MediaDrm is provisioned for |origin|.
+  OnProvisioned() => (bool success);
+
+  // Saves persistent session data for |session_id|.
+  SavePersistentSession(
+    string session_id, array<uint8> key_set_id, string mime_type)

[dcheng, 2017/03/29 01:17:23]

One alternative is to package key_set_id and mime_type in a mojo struct.

[xhwang, 2017/03/29 20:47:25]

That's what I started with :)

But with only two values in the struct, I found it's actually making code more
complex so I gave up. Please let me know if feel strong about this.

[dcheng, 2017/03/29 21:15:12]

Hm... why did it make it more complex? Once we have the struct here, can't we
just pass around session_data.key_id and session_data.mime_type directly?

[xhwang, 2017/03/29 21:30:44]

Sure, let me give it another try.

[xhwang, 2017/03/30 00:04:23]

Done.

+    => (bool success);
+
+  // Loads persistent session data for |session_id|.
+  // Upon |success|, |key_set_id| and |mime_type| must not be empty. Otherwise,
+  // |key_set_id| and |mime_type| must be empty.
+  LoadPersistentSession(string session_id)
+    => (bool success, array<uint8> key_set_id, string mime_type);

[dcheng, 2017/03/29 01:17:23]

Then here we can just return SessionData? here, and avoid the need for bool
success + the two members

[xhwang, 2017/03/29 20:47:25]

ditto. I actually like to have |success| here to be consistent with other
methods. But I agree if we use the struct then it's not necessary.

[dcheng, 2017/03/29 21:15:12]

Really, the primary value is here: then we only need a single return value, and
we can guarantee that the result is consistent.

[xhwang, 2017/03/29 21:30:44]

Acknowledged.

+
+  // Removes the persistent session data for |session_id|.
+  RemovePersistentSession(string session_id) => (bool success);
+};