Add Promises for EME (Chromium side)

media/base/media_keys_session_promise.h

+// 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.
+
+#ifndef MEDIA_BASE_MEDIA_KEYS_SESSION_PROMISE_H_
+#define MEDIA_BASE_MEDIA_KEYS_SESSION_PROMISE_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/callback.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+typedef base::Callback<void()> PromiseResolvedCB;
+
+typedef base::Callback<void(const std::string& web_session_id)>
+    PromiseResolvedWithSessionCB;
+
+typedef base::Callback<void(const std::string& error_name,
+                            uint32 system_code,
+                            const std::string& error_message)>
+    PromiseRejectedCB;
+
+// Interface for promises being resolved/rejected in response to various
+// session actions. These may be called synchronously or asynchronously.

[ddorwin, 2014/05/05 18:35:42]

Sync is fine as long as we enforce async, which we probably do by posting a task
somewhere.

+// Only one method may be called on any promise. It is expected that the
+// caller free the promise once it is resolved/rejected.
+class MEDIA_EXPORT MediaKeysSessionPromise {

[ddorwin, 2014/05/05 18:35:42]

The non-session promises are on MKS, but the session promises are on MK. Maybe
you can use that or what they do as a difference in the names (see below).

[ddorwin, 2014/05/05 18:44:45]

FYI, MediaKeys.setServerCertificate() is now an exception to this.

+ public:
+  MediaKeysSessionPromise(PromiseResolvedCB resolve_cb,

[ddorwin, 2014/05/05 18:35:42]

It's odd to be passing two different resolve options when only one can ever be
called by the receiver. Same with the two methods below. We should have separate
classes, use templates, or something.

[jrummell, 2014/05/08 23:37:45]

Done.

+                          PromiseResolvedWithSessionCB resolve_with_session_cb,
+                          PromiseRejectedCB rejected_cb);
+  virtual ~MediaKeysSessionPromise();

[ddorwin, 2014/05/05 18:35:42]

None of these need to be virtual.

[jrummell, 2014/05/08 23:37:45]

The promises are overridden in a couple of places (tests, for example). I get
errors if they're not virtual.

+
+  // Used to indicate that UpdateSession()/ReleaseSession() has successfully
+  // completed.
+  virtual void resolve();
+
+  // Used to indicate that CreateSession()/LoadSession() has successfully
+  // completed. |web_session_id| is the ID of the new session created.
+  virtual void resolve(const std::string& web_session_id);

[xhwang, 2014/05/05 20:46:42]

It's odd to pass Promises with two resolve() functions and only one should be
used. Maybe we should split this to two Promise classes.

[jrummell, 2014/05/08 23:37:45]

Done.

+
+  // Used to indicate that the operation failed. |error_name| should match one
+  // of the W3C DOM error names (http://www.w3.org/TR/dom/#error-names-table).
+  // |system_code| is a Key System-specific value for the error that occurred,
+  // or 0 if there is no associated status code or such status codes are not
+  // supported by the Key System. |error_message| is optional.
+  virtual void reject(const std::string& error_name,
+                      uint32 system_code,
+                      const std::string& error_message);
+
+ protected:
+  MediaKeysSessionPromise();
+
+ private:
+  PromiseResolvedCB resolve_cb_;
+  PromiseResolvedWithSessionCB resolve_with_session_cb_;
+  PromiseRejectedCB rejected_cb_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaKeysSessionPromise);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_MEDIA_KEYS_SESSION_PROMISE_H_