Add Promises for EME (Chromium side)

media/base/media_keys_session_promise.cc

Index: media/base/media_keys_session_promise.cc
diff --git a/media/base/media_keys_session_promise.cc b/media/base/media_keys_session_promise.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e0762910b1b29aa6800315fe7f8980fe13fc0e16
--- /dev/null
+++ b/media/base/media_keys_session_promise.cc
@@ -0,0 +1,45 @@
+// 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.
+
+#include "media/base/media_keys_session_promise.h"
+
+namespace media {
+
+MediaKeysSessionPromise::MediaKeysSessionPromise() {}
+
+MediaKeysSessionPromise::MediaKeysSessionPromise(
+    PromiseResolvedCB resolve_cb,
+    PromiseResolvedWithSessionCB resolve_with_session_cb,
+    PromiseRejectedCB rejected_cb)
+    : resolve_cb_(resolve_cb),
+      resolve_with_session_cb_(resolve_with_session_cb),
+      rejected_cb_(rejected_cb) {
+  DCHECK(!resolve_cb.is_null() || !resolve_with_session_cb.is_null());
+  DCHECK(!rejected_cb_.is_null());
+}
+
+MediaKeysSessionPromise::~MediaKeysSessionPromise() {

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

We should be able to DCHECK that the promise is already resolved or rejected
upon destruction. Then we can make sure there are no outstanding promises.

To do this, we can either have a flag "is_pending" to indicate whether this
promise is still "pending", or by using ResetAndReturn(&xxx_cb_).Run() when we
resolve or reject the promises. Since we have multiple callbacks, having a flag
might be easier/cleaner.

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

Good idea. Done.

+}
+
+void MediaKeysSessionPromise::resolve() {
+  if (!resolve_cb_.is_null())
+    resolve_cb_.Run();
+  else
+    reject("InvalidStateError", 0, std::string());

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

When could this happen? Shall we just DCHECK(!resolve_cb_.is_null())?

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

Not needed anymore now that the classes are done by a template.

+}
+
+void MediaKeysSessionPromise::resolve(const std::string& web_session_id) {
+  if (!resolve_with_session_cb_.is_null())
+    resolve_with_session_cb_.Run(web_session_id);
+  else
+    reject("InvalidStateError", 0, std::string());
+}
+
+void MediaKeysSessionPromise::reject(const std::string& error_name,
+                                     uint32 system_code,
+                                     const std::string& error_message) {
+  rejected_cb_.Run(error_name, system_code, error_message);
+}
+
+}  // namespace media