Allow JSON messages to be returned for ClearKey.

LayoutTests/media/encrypted-media/encrypted-media-utils.js

 var console = null;
 
 function consoleWrite(text)
 {
     if (!console && document.body) {
         console = document.createElement('div');
         document.body.appendChild(console);
     }
     var span = document.createElement('span');
     span.appendChild(document.createTextNode(text));
@@ skipping 105 matching lines @@
     // currently no way to report a failed test in the test harness, errors
     // are reported using force_timeout().
     if (message)
         consoleWrite(message + ': ' + error.message);
     else if (error)
         consoleWrite(error.message);
 
     test.force_timeout();
     test.done();
 }
+
+function extractSingleKeyIdFromMessage(message)
+{
+    try {
+        var json = JSON.parse(String.fromCharCode.apply(null, new Uint8Array(message)));
+        // Decode the first element of 'kids'.
+        // FIXME: Switch to base64url. See
+        // https://dvcs.w3.org/hg/html-media/raw-file/default/encrypted-media/encrypted-media.html#using-base64url
+        assert_equals(1, json.kids.length);
+        var decoded_key = atob(json.kids[0]);
+        // Convert to an Uint8Array and return it.
+        return stringToUint8Array(decoded_key);
+    }
+    catch (o) {
+        // Not valid JSON, so return message untouched as Uint8Array.
+        // This is for backwards compatibility.
+        // FIXME: Remove this once the code is switched to return JSON all
+        // the time.
+        return new Uint8Array(message);
+    }
+}