Clarify wording of MediaCrypto exception "ERROR_NO_KEY"

related-to-bug: 20857014
Change-Id: I13204528ec44cda76a721f4d9f6021c1435921ac
diff --git a/media/java/android/media/MediaCodec.java b/media/java/android/media/MediaCodec.java
index d22cfda..d47bedc 100644
--- a/media/java/android/media/MediaCodec.java
+++ b/media/java/android/media/MediaCodec.java
@@ -902,9 +902,9 @@
         }
 
         /**
-         * This indicates that no key has been set to perform the requested
-         * decrypt operation.  The operation can be retried after adding
-         * a decryption key.
+         * This indicates that the requested key was not found when trying to
+         * perform a decrypt operation.  The operation can be retried after adding
+         * the correct decryption key.
          */
         public static final int ERROR_NO_KEY = 1;