Change how MatrixEvent manages encrypted events

Make `MatrixEvent.event` contain the *encrypted* event, and keep the plaintext
payload in a separate `_clearEvent` property.

This achieves several aims:

* means that we have a record of the actual object which was received over
  the wire, which can be shown by clients for 'view source'.

* makes sent and received encrypted MatrixEvents more consistent (previously
  sent ones had `encryptedType` and `encryptedContent` properties, whereas
  received ones threw away the ciphertext).

* Avoids having to make two MatrixEvents in the receive path, and copying
  fields from one to the other.

*Hopefully* most clients have followed the advice given in the jsdoc of not
relying on MatrixEvent.event to get at events. If they haven't, I guess they'll
break in the face of encrypted events.

(The pushprocessor didn't follow this advice, so needed some tweaks.)

lib/client.js

@@ -1159,11 +1159,7 @@ function _encryptEventIfNeeded(client, event) {
     var encryptedContent = _encryptMessage(
         client, roomId, e2eRoomInfo, event.getType(), event.getContent()
     );
-    event.encryptedType = "m.room.encrypted";
-    event.encryptedContent = encryptedContent;
-    // TODO: Specify this in the event constructor rather than fiddling
-    // with the event object internals.
-    event.encrypted = true;
+    event.makeEncrypted("m.room.encrypted", encryptedContent);
 }
 
 function _encryptMessage(client, roomId, e2eRoomInfo, eventType, content) {
@@ -1230,15 +1226,13 @@ function _encryptMessage(client, roomId, e2eRoomInfo, eventType, content) {
     }
 }
 
-
 /**
  * Decrypt a received event according to the algorithm specified in the event.
  *
  * @param {MatrixClient} client
- * @param {MatrixEvent} event
+ * @param {object} raw event
  *
- * @return {MatrixEvent} a new MatrixEvent
- * @private
+ * @return {object} decrypted payload (with properties 'type', 'content')
  */
 function _decryptMessage(client, event) {
     if (client.sessionStore === null || !CRYPTO_ENABLED) {
@@ -1247,7 +1241,7 @@ function _decryptMessage(client, event) {
         return _badEncryptedMessage(event, "**Encryption not enabled**");
     }
 
-    var content = event.getContent();
+    var content = event.content;
     if (content.algorithm === OLM_ALGORITHM) {
         var deviceKey = content.sender_key;
         var ciphertext = content.ciphertext;
@@ -1295,16 +1289,7 @@ function _decryptMessage(client, event) {
         // TODO: Check the sender user id matches the sender key.
 
         if (payloadString !== null) {
-            var payload = JSON.parse(payloadString);
-            return new MatrixEvent({
-                origin_server_ts: event.getTs(),
-                room_id: payload.room_id,
-                user_id: event.getSender(),
-                event_id: event.getId(),
-                unsigned: event.getUnsigned(),
-                type: payload.type,
-                content: payload.content,
-            }, event);
+            return JSON.parse(payloadString);
         } else {
             return _badEncryptedMessage(event, "**Bad Encrypted Message**");
         }
@@ -1313,20 +1298,14 @@ function _decryptMessage(client, event) {
 }
 
 function _badEncryptedMessage(event, reason) {
-    return new MatrixEvent({
+    return {
         type: "m.room.message",
-        // TODO: Add rest of the event keys.
-        origin_server_ts: event.getTs(),
-        room_id: event.getRoomId(),
-        user_id: event.getSender(),
-        event_id: event.getId(),
-        unsigned: event.getUnsigned(),
         content: {
             msgtype: "m.bad.encrypted",
             body: reason,
-            content: event.getContent()
-        }
-    }, event);
+            content: event.content,
+        },
+    };
 }
 
 // encrypts the event if necessary
@@ -1957,7 +1936,7 @@ function _membershipChange(client, roomId, userId, membership, reason, callback)
 MatrixClient.prototype.getPushActionsForEvent = function(event) {
     if (event._pushActions === undefined) {
         var pushProcessor = new PushProcessor(this);
-        event._pushActions = pushProcessor.actionsForEvent(event.event);
+        event._pushActions = pushProcessor.actionsForEvent(event);
     }
     return event._pushActions;
 };
@@ -3526,12 +3505,11 @@ function _resolve(callback, defer, res) {
 
 function _PojoToMatrixEventMapper(client) {
     function mapper(plainOldJsObject) {
-        var event = new MatrixEvent(plainOldJsObject);
-        if (event.getType() === "m.room.encrypted") {
-            return _decryptMessage(client, event);
-        } else {
-            return event;
+        var clearData;
+        if (plainOldJsObject.type === "m.room.encrypted") {
+            clearData = _decryptMessage(client, plainOldJsObject);
         }
+        return new MatrixEvent(plainOldJsObject, clearData);
     }
     return mapper;
 }