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..2fdcc5b42f9feb15e63105f4c817fbec0f95696f 100644
--- a/media/base/decryptor.h
+++ b/media/base/decryptor.h
@@ -204,6 +204,17 @@ class MEDIA_EXPORT Decryptor {
   DISALLOW_COPY_AND_ASSIGN(Decryptor);
 };
 
+// Callback to notify that a decryptor is ready.
+typedef base::Callback<void(Decryptor*)> DecryptorReadyCB;
+// Callback to request/cancel notification that a decryptor is ready.
+// Calling this callback with a non-null callback registers decryptor ready
+// notification. When the decryptor is ready, notification will be sent
+// through the provided callback.
+// Calling this callback with a null callback cancels previously registered
+// decryptor ready notification. Any previously provided callback will be
+// fired immediately with NULL.
+typedef base::Callback<void(const DecryptorReadyCB&)> SetDecryptorReadyCB;
+
 }  // namespace media
 
 #endif  // MEDIA_BASE_DECRYPTOR_H_