Address a number of review comments.

Make sure that room state is copied correctly when resetting the live
timeline.

Also comments and bits.

lib/models/event-timeline.js

@@ -5,6 +5,8 @@
  */
 
 var RoomState = require("./room-state");
+var utils = require("../utils");
+var MatrixEvent = require("./event").MatrixEvent;
 
 /**
  * Construct a new EventTimeline
@@ -31,7 +33,9 @@ function EventTimeline(roomId) {
     this._events = [];
     this._baseIndex = -1;
     this._startState = new RoomState(roomId);
+    this._startState.paginationToken = null;
     this._endState = new RoomState(roomId);
+    this._endState.paginationToken = null;
 
     this._prevTimeline = null;
     this._nextTimeline = null;
@@ -54,8 +58,14 @@ EventTimeline.prototype.initialiseState = function(stateEvents) {
         throw new Error("Cannot initialise state after events are added");
     }
 
-    // do we need to copy here? sync thinks we do but I can't see why
-    this._startState.setStateEvents(stateEvents);
+    // we deep-copy the events here, in case they get changed later - we don't
+    // want changes to the start state leaking through to the end state.
+    var oldStateEvents = utils.map(
+        utils.deepCopy(
+            stateEvents.map(function(mxEvent) { return mxEvent.event; })
+        ), function(ev) { return new MatrixEvent(ev); });
+
+    this._startState.setStateEvents(oldStateEvents);
     this._endState.setStateEvents(stateEvents);
 };
 
@@ -72,7 +82,9 @@ EventTimeline.prototype.getRoomId = function() {
  *
  * <p>This is an index which is incremented when events are prepended to the
  * timeline. An individual event therefore stays at the same index in the array
- * relative to the base index.
+ * relative to the base index (although note that a given event's index may
+ * well be less than the base index, thus giving that event a negative relative
+ * index).
  *
  * @return {number}
  */