Refactor decryption

Create the MatrixEvent wrapper before decryption, and then pass that into the
decryptors, which should update it.

Also remove the workaround that sends m.new_device messages when we get an
unknown session; it's just a bandaid which is obscuring more meaningful
problems.

lib/client.js

@@ -463,38 +463,31 @@ MatrixClient.prototype.isRoomEncrypted = function(roomId) {
  * Decrypt a received event according to the algorithm specified in the event.
  *
  * @param {MatrixClient} client
- * @param {object} raw event
- *
- * @return {MatrixEvent}
+ * @param {MatrixEvent} event
  */
 function _decryptEvent(client, event) {
     if (!client._crypto) {
-        return _badEncryptedMessage(event, "**Encryption not enabled**");
+        _badEncryptedMessage(event, "**Encryption not enabled**");
+        return;
     }
 
-    var decryptionResult;
     try {
-        decryptionResult = client._crypto.decryptEvent(event);
+        client._crypto.decryptEvent(event);
     } catch (e) {
         if (!(e instanceof Crypto.DecryptionError)) {
             throw e;
         }
-        return _badEncryptedMessage(event, "**" + e.message + "**");
+        _badEncryptedMessage(event, "**" + e.message + "**");
+        return;
     }
-    return new MatrixEvent(
-        event, decryptionResult.payload,
-        decryptionResult.keysProved,
-        decryptionResult.keysClaimed
-    );
 }
 
 function _badEncryptedMessage(event, reason) {
-    return new MatrixEvent(event, {
+    event.setClearData({
         type: "m.room.message",
         content: {
             msgtype: "m.bad.encrypted",
             body: reason,
-            content: event.content,
         },
     });
 }
@@ -2829,10 +2822,11 @@ function _resolve(callback, defer, res) {
 
 function _PojoToMatrixEventMapper(client) {
     function mapper(plainOldJsObject) {
-        if (plainOldJsObject.type === "m.room.encrypted") {
-            return _decryptEvent(client, plainOldJsObject);
+        var event = new MatrixEvent(plainOldJsObject);
+        if (event.isEncrypted()) {
+            _decryptEvent(client, event);
         }
-        return new MatrixEvent(plainOldJsObject);
+        return event;
     }
     return mapper;
 }