Allow JSON messages to be returned for ClearKey.

LayoutTests/media/encrypted-media/encrypted-media-lifetime-reload.html

Index: LayoutTests/media/encrypted-media/encrypted-media-lifetime-reload.html
diff --git a/LayoutTests/media/encrypted-media/encrypted-media-lifetime-reload.html b/LayoutTests/media/encrypted-media/encrypted-media-lifetime-reload.html
index 5590a6bd87c49a1f06c34a3552044470dbcc0147..1a80d6de3c17a1abfe81c6012e2ab812ca8eed3d 100644
--- a/LayoutTests/media/encrypted-media/encrypted-media-lifetime-reload.html
+++ b/LayoutTests/media/encrypted-media/encrypted-media-lifetime-reload.html
@@ -47,7 +47,7 @@
                     assert_equals(event.target, mediaKeySession);
                     assert_equals(event.type, 'message');
 
-                    var keyId = new Uint8Array(event.message);
+                    var keyId = extractFirstLicenseKey(event.message);

[ddorwin, 2014/08/08 20:41:14]

extractSingleKeyIdFromMessage()?
If there is more than one, we probably shouldn't be calling this function.

Maybe someday we'll have extractKeyIdsFromMessage() and pass the entire list to
createJWKSet.

[jrummell, 2014/08/08 23:51:28]

Done.

                     var jwkSet = stringToUint8Array(createJWKSet(createJWK(keyId, rawKey)));
                     mediaKeySession.update(jwkSet).then(function(result) {
                         sessionReadyReceived = true;