Encrypted Media: Support Audio Decrypt-Only.

media/base/decryptor.h

Index: media/base/decryptor.h
diff --git a/media/base/decryptor.h b/media/base/decryptor.h
index 87c275d7a845ea7d4447d7dcefac4bdbb61fab25..1a19349eaeaae2bdfd61bf996695af1e6af30304 100644
--- a/media/base/decryptor.h
+++ b/media/base/decryptor.h
@@ -204,6 +204,18 @@ class MEDIA_EXPORT Decryptor {
   DISALLOW_COPY_AND_ASSIGN(Decryptor);
 };
 
+// Callback to notify decryptor creation.
+typedef base::Callback<void(Decryptor*)> DecryptorNotificationCB;
+// Callback to request/cancel decryptor creation notification.
+// Calling this callback with a non-null callback registers decryptor creation
+// notification. When the decryptor is created, notification will be sent
+// through the provided callback.
+// Calling this callback with a null callback cancels previously registered
+// decryptor creation notification. Any previously provided callback will be
+// fired immediately with NULL.
+typedef base::Callback<void(const DecryptorNotificationCB&)>
+    RequestDecryptorNotificationCB;
+
 }  // namespace media
 
 #endif  // MEDIA_BASE_DECRYPTOR_H_